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Need help with query

P: n/a
I need to extract data from this table to find the lowest prices of
each product as of today. The product will be listed/grouped by the
name only, discarding the product code - I use SUBSTRING(ProductName,
1, CHARINDEX('(', ProductName)-2).

I can get this result, but I had to use several views (totally
inefficient). I think this can be done in one efficient/fast query,
but I can't think of one.

In the case that one query is not possible, is there other efficient
way to get the results? There are about 300K records in the table.

Any help is appreciated! Thanks a lot in advance!

Thanks,
Netpurpose

-----------------------START TABLE INFO-------------------------

Here is the desired result (on 8/29/03):

ProductName Price
---------------------------------------- ---------------------
Product One 33.5000
Product Three 40.4500
Product Two 44.7500
Here is the table info:

CREATE TABLE [ProductList] (
[Distributor] [nvarchar] (5) NULL ,
[ProductName] [nvarchar] (40) NULL ,
[Price] [money] NULL ,
[EffectiveDate] [smalldatetime] NULL
) ON [PRIMARY]
Table Data (comma delimited):
*Sorry I can't list in insert commands as there are too many.

"Manufacturer","ProductName","Price","EffectiveDat e"
"AAA","Product One (MXT234)",1000,2003-08-30 00:00:00
"BBB","Product One (MXT234)",1000,2003-07-29 00:00:00
"BBB","Product One (MXT234)",28.15,2003-07-30 00:00:00
"BBB","Product One (MXT234)",35.22,2003-08-04 00:00:00
"BBB","Product One (MXT234)",35.22,2003-08-04 00:00:00
"BBB","Product One (MXT234)",1000,2003-08-16 00:00:00
"BBB","Product One (MXT234)",33.8,2003-08-27 00:00:00
"CCC","Product One (MXT234)",33.25,2003-08-31 00:00:00
"DDD","Product One (MXT234)",46.25,2003-01-02 00:00:00
"EEE","Product One (MXT234)",1000,2003-08-30 00:00:00
"FFF","Product One (MXT234)",1000,2003-08-30 00:00:00
"GGG","Product One (MXT234)",1000,2003-09-01 00:00:00
"HHH","Product One (MXT234)",33.8,2003-08-04 00:00:00
"III","Product One (MXT234)",1000,2003-01-13 00:00:00
"JJJ","Product One (MXT234)",34.35,2003-07-30 00:00:00
"JJJ","Product One (MXT234)",34.35,2003-09-01 00:00:00
"KKK","Product One (MXT234)",1000,2003-08-30 00:00:00
"ZZZ","Product One (MXT205)",54,2003-01-13 00:00:00
"AAA","Product One (MXT205)",1000,2003-08-30 00:00:00
"BBB","Product One (MXT205)",33.95,2003-07-27 00:00:00
"BBB","Product One (MXT205)",33.95,2003-07-29 00:00:00
"BBB","Product One (MXT205)",35.22,2003-08-04 00:00:00
"BBB","Product One (MXT205)",33.8,2003-08-16 00:00:00
"BBB","Product One (MXT205)",33.5,2003-08-27 00:00:00
"CCC","Product One (MXT205)",1000,2003-08-30 00:00:00
"DDD","Product One (MXT205)",46.25,2003-01-02 00:00:00
"EEE","Product One (MXT205)",1000,2003-08-30 00:00:00
"FFF","Product One (MXT205)",1000,2003-08-30 00:00:00
"GGG","Product One (MXT205)",1000,2003-09-01 00:00:00
"HHH","Product One (MXT205)",33.95,2003-08-04 00:00:00
"III","Product One (MXT205)",1000,2003-01-13 00:00:00
"JJJ","Product One (MXT205)",34.35,2003-07-30 00:00:00
"JJJ","Product One (MXT205)",34.35,2003-09-01 00:00:00
"KKK","Product One (MXT205)",1000,2003-08-30 00:00:00
"ZZZ","Product One (MXT548)",54,2003-01-13 00:00:00
"AAA","Product One (MXT548)",25.04,2003-08-31 00:00:00
"BBB","Product One (MXT548)",33.95,2003-07-22 00:00:00
"BBB","Product One (MXT548)",33.95,2003-07-27 00:00:00
"BBB","Product One (MXT548)",35.22,2003-08-04 00:00:00
"BBB","Product One (MXT548)",33.8,2003-08-16 00:00:00
"BBB","Product One (MXT548)",33.8,2003-08-27 00:00:00
"CCC","Product One (MXT548)",1000,2003-08-30 00:00:00
"DDD","Product One (MXT548)",46.25,2003-01-02 00:00:00
"EEE","Product One (MXT548)",1000,2003-08-30 00:00:00
"FFF","Product One (MXT548)",1000,2003-08-30 00:00:00
"GGG","Product One (MXT548)",1000,2003-09-01 00:00:00
"HHH","Product One (MXT548)",33.8,2003-08-04 00:00:00
"III","Product One (MXT548)",1000,2003-01-13 00:00:00
"JJJ","Product One (MXT548)",34.35,2003-07-30 00:00:00
"JJJ","Product One (MXT548)",34.35,2003-09-01 00:00:00
"KKK","Product One (MXT548)",1000,2003-08-30 00:00:00
"ZZZ","Product Two (DGT6789)",54,2003-01-13 00:00:00
"AAA","Product Two (DGT6789)",1000,2003-08-30 00:00:00
"BBB","Product Two (DGT6789)",1000,2003-07-22 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-07-27 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-07-29 00:00:00
"BBB","Product Two (DGT6789)",44.35,2003-07-30 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-08-04 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-08-04 00:00:00
"BBB","Product Two (DGT6789)",1000,2003-08-23 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-08-27 00:00:00
"CCC","Product Two (DGT6789)",1000,2003-08-30 00:00:00
"DDD","Product Two (DGT6789)",46.25,2003-05-08 00:00:00
"EEE","Product Two (DGT6789)",1000,2003-08-30 00:00:00
"FFF","Product Two (DGT6789)",1000,2003-08-30 00:00:00
"GGG","Product Two (DGT6789)",1000,2003-09-01 00:00:00
"HHH","Product Two (DGT6789)",46.1,2003-08-04 00:00:00
"III","Product Two (DGT6789)",1000,2003-01-13 00:00:00
"JJJ","Product Two (DGT6789)",47.45,2003-08-04 00:00:00
"JJJ","Product Two (DGT6789)",47.45,2003-09-01 00:00:00
"KKK","Product Two (DGT6789)",44.75,2003-07-14 00:00:00
"ZZZ","Product Two (DGT6704)",54,2003-01-13 00:00:00
"AAA","Product Two (DGT6704)",1000,2003-08-30 00:00:00
"BBB","Product Two (DGT6704)",45.5,2003-07-22 00:00:00
"BBB","Product Two (DGT6704)",46.1,2003-08-04 00:00:00
"BBB","Product Two (DGT6704)",46.1,2003-08-16 00:00:00
"BBB","Product Two (DGT6704)",44.75,2003-08-27 00:00:00
"CCC","Product Two (DGT6704)",1000,2003-08-30 00:00:00
"DDD","Product Two (DGT6704)",46.25,2003-05-08 00:00:00
"EEE","Product Two (DGT6704)",1000,2003-08-30 00:00:00
"FFF","Product Two (DGT6704)",1000,2003-08-30 00:00:00
"GGG","Product Two (DGT6704)",1000,2003-09-01 00:00:00
"HHH","Product Two (DGT6704)",46.1,2003-08-04 00:00:00
"III","Product Two (DGT6704)",1000,2003-01-13 00:00:00
"JJJ","Product Two (DGT6704)",47.45,2003-08-04 00:00:00
"JJJ","Product Two (DGT6704)",47.45,2003-09-01 00:00:00
"KKK","Product Two (DGT6704)",44.75,2003-07-14 00:00:00
"ZZZ","Product Three (QAT6785)",52,2003-01-13 00:00:00
"AAA","Product Three (QAT6785)",1000,2003-08-30 00:00:00
"BBB","Product Three (QAT6785)",45.5,2003-07-22 00:00:00
"BBB","Product Three (QAT6785)",532.25,2003-07-29 00:00:00
"BBB","Product Three (QAT6785)",1000,2003-07-30 00:00:00
"BBB","Product Three (QAT6785)",1000,2003-08-04 00:00:00
"BBB","Product Three (QAT6785)",46.1,2003-08-16 00:00:00
"BBB","Product Three (QAT6785)",44.75,2003-08-27 00:00:00
"CCC","Product Three (QAT6785)",42.65,2003-08-31 00:00:00
"DDD","Product Three (QAT6785)",46.25,2003-05-08 00:00:00
"EEE","Product Three (QAT6785)",1000,2003-08-30 00:00:00
"FFF","Product Three (QAT6785)",1000,2003-08-30 00:00:00
"GGG","Product Three (QAT6785)",1000,2003-09-01 00:00:00
"HHH","Product Three (QAT6785)",46.1,2003-08-04 00:00:00
"III","Product Three (QAT6785)",1000,2003-01-13 00:00:00
"JJJ","Product Three (QAT6785)",40.45,2003-08-04 00:00:00
"JJJ","Product Three (QAT6785)",40.45,2003-09-01 00:00:00
"KKK","Product Three (QAT6785)",44.75,2003-07-14 00:00:00
"ZZZ","Product Three (QAT556)",50.23,2003-01-13 00:00:00
"AAA","Product Three (QAT556)",1000,2003-08-30 00:00:00
"BBB","Product Three (QAT556)",44.75,2003-07-22 00:00:00
"BBB","Product Three (QAT556)",532.25,2003-07-29 00:00:00
"BBB","Product Three (QAT556)",1000,2003-07-30 00:00:00
"BBB","Product Three (QAT556)",1000,2003-08-03 00:00:00
"BBB","Product Three (QAT556)",1000,2003-08-04 00:00:00
"BBB","Product Three (QAT556)",44.75,2003-08-16 00:00:00
"BBB","Product Three (QAT556)",44.75,2003-08-27 00:00:00
"CCC","Product Three (QAT556)",1000,2003-08-30 00:00:00
"DDD","Product Three (QAT556)",46.25,2003-05-08 00:00:00
"EEE","Product Three (QAT556)",1000,2003-08-30 00:00:00
"FFF","Product Three (QAT556)",1000,2003-08-30 00:00:00
"GGG","Product Three (QAT556)",1000,2003-09-01 00:00:00
"HHH","Product Three (QAT556)",46.1,2003-08-04 00:00:00
"III","Product Three (QAT556)",1000,2003-01-13 00:00:00
"JJJ","Product Three (QAT556)",40.45,2003-08-04 00:00:00
"JJJ","Product Three (QAT556)",40.45,2003-09-01 00:00:00
"KKK","Product Three (QAT556)",44.75,2003-07-14 00:00:00
"JJJ","Product Three (QAT556)",40.15,2003-08-01 00:00:00
Jul 20 '05 #1
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9 Replies


P: n/a
"netpurpose" <ne********@hotmail.com> wrote in message
news:31**************************@posting.google.c om...
I need to extract data from this table to find the lowest prices of
each product as of today. The product will be listed/grouped by the
name only, discarding the product code - I use SUBSTRING(ProductName,
1, CHARINDEX('(', ProductName)-2).

I can get this result, but I had to use several views (totally
inefficient). I think this can be done in one efficient/fast query,
but I can't think of one.

In the case that one query is not possible, is there other efficient
way to get the results? There are about 300K records in the table.

Any help is appreciated! Thanks a lot in advance!

Thanks,
Netpurpose
SELECT P1.ProductName, P1.Price
FROM ProductList AS P1
WHERE EffectiveDate <= CURRENT_TIMESTAMP AND
NOT EXISTS
(SELECT *
FROM ProductList AS P2
WHERE SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) =
SUBSTRING(P2.ProductName, 1,
CHARINDEX('(', P2.ProductName) - 2) AND
P2.EffectiveDate <= CURRENT_TIMESTAMP AND
P2.Price < P1.Price)

Regards,
jag

-----------------------START TABLE INFO-------------------------

Here is the desired result (on 8/29/03):

ProductName Price
---------------------------------------- ---------------------
Product One 33.5000
Product Three 40.4500
Product Two 44.7500
Here is the table info:

CREATE TABLE [ProductList] (
[Distributor] [nvarchar] (5) NULL ,
[ProductName] [nvarchar] (40) NULL ,
[Price] [money] NULL ,
[EffectiveDate] [smalldatetime] NULL
) ON [PRIMARY]
Table Data (comma delimited):
*Sorry I can't list in insert commands as there are too many.

"Manufacturer","ProductName","Price","EffectiveDat e"
"AAA","Product One (MXT234)",1000,2003-08-30 00:00:00
"BBB","Product One (MXT234)",1000,2003-07-29 00:00:00
"BBB","Product One (MXT234)",28.15,2003-07-30 00:00:00
"BBB","Product One (MXT234)",35.22,2003-08-04 00:00:00
"BBB","Product One (MXT234)",35.22,2003-08-04 00:00:00
"BBB","Product One (MXT234)",1000,2003-08-16 00:00:00
"BBB","Product One (MXT234)",33.8,2003-08-27 00:00:00
"CCC","Product One (MXT234)",33.25,2003-08-31 00:00:00
"DDD","Product One (MXT234)",46.25,2003-01-02 00:00:00
"EEE","Product One (MXT234)",1000,2003-08-30 00:00:00
"FFF","Product One (MXT234)",1000,2003-08-30 00:00:00
"GGG","Product One (MXT234)",1000,2003-09-01 00:00:00
"HHH","Product One (MXT234)",33.8,2003-08-04 00:00:00
"III","Product One (MXT234)",1000,2003-01-13 00:00:00
"JJJ","Product One (MXT234)",34.35,2003-07-30 00:00:00
"JJJ","Product One (MXT234)",34.35,2003-09-01 00:00:00
"KKK","Product One (MXT234)",1000,2003-08-30 00:00:00
"ZZZ","Product One (MXT205)",54,2003-01-13 00:00:00
"AAA","Product One (MXT205)",1000,2003-08-30 00:00:00
"BBB","Product One (MXT205)",33.95,2003-07-27 00:00:00
"BBB","Product One (MXT205)",33.95,2003-07-29 00:00:00
"BBB","Product One (MXT205)",35.22,2003-08-04 00:00:00
"BBB","Product One (MXT205)",33.8,2003-08-16 00:00:00
"BBB","Product One (MXT205)",33.5,2003-08-27 00:00:00
"CCC","Product One (MXT205)",1000,2003-08-30 00:00:00
"DDD","Product One (MXT205)",46.25,2003-01-02 00:00:00
"EEE","Product One (MXT205)",1000,2003-08-30 00:00:00
"FFF","Product One (MXT205)",1000,2003-08-30 00:00:00
"GGG","Product One (MXT205)",1000,2003-09-01 00:00:00
"HHH","Product One (MXT205)",33.95,2003-08-04 00:00:00
"III","Product One (MXT205)",1000,2003-01-13 00:00:00
"JJJ","Product One (MXT205)",34.35,2003-07-30 00:00:00
"JJJ","Product One (MXT205)",34.35,2003-09-01 00:00:00
"KKK","Product One (MXT205)",1000,2003-08-30 00:00:00
"ZZZ","Product One (MXT548)",54,2003-01-13 00:00:00
"AAA","Product One (MXT548)",25.04,2003-08-31 00:00:00
"BBB","Product One (MXT548)",33.95,2003-07-22 00:00:00
"BBB","Product One (MXT548)",33.95,2003-07-27 00:00:00
"BBB","Product One (MXT548)",35.22,2003-08-04 00:00:00
"BBB","Product One (MXT548)",33.8,2003-08-16 00:00:00
"BBB","Product One (MXT548)",33.8,2003-08-27 00:00:00
"CCC","Product One (MXT548)",1000,2003-08-30 00:00:00
"DDD","Product One (MXT548)",46.25,2003-01-02 00:00:00
"EEE","Product One (MXT548)",1000,2003-08-30 00:00:00
"FFF","Product One (MXT548)",1000,2003-08-30 00:00:00
"GGG","Product One (MXT548)",1000,2003-09-01 00:00:00
"HHH","Product One (MXT548)",33.8,2003-08-04 00:00:00
"III","Product One (MXT548)",1000,2003-01-13 00:00:00
"JJJ","Product One (MXT548)",34.35,2003-07-30 00:00:00
"JJJ","Product One (MXT548)",34.35,2003-09-01 00:00:00
"KKK","Product One (MXT548)",1000,2003-08-30 00:00:00
"ZZZ","Product Two (DGT6789)",54,2003-01-13 00:00:00
"AAA","Product Two (DGT6789)",1000,2003-08-30 00:00:00
"BBB","Product Two (DGT6789)",1000,2003-07-22 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-07-27 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-07-29 00:00:00
"BBB","Product Two (DGT6789)",44.35,2003-07-30 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-08-04 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-08-04 00:00:00
"BBB","Product Two (DGT6789)",1000,2003-08-23 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-08-27 00:00:00
"CCC","Product Two (DGT6789)",1000,2003-08-30 00:00:00
"DDD","Product Two (DGT6789)",46.25,2003-05-08 00:00:00
"EEE","Product Two (DGT6789)",1000,2003-08-30 00:00:00
"FFF","Product Two (DGT6789)",1000,2003-08-30 00:00:00
"GGG","Product Two (DGT6789)",1000,2003-09-01 00:00:00
"HHH","Product Two (DGT6789)",46.1,2003-08-04 00:00:00
"III","Product Two (DGT6789)",1000,2003-01-13 00:00:00
"JJJ","Product Two (DGT6789)",47.45,2003-08-04 00:00:00
"JJJ","Product Two (DGT6789)",47.45,2003-09-01 00:00:00
"KKK","Product Two (DGT6789)",44.75,2003-07-14 00:00:00
"ZZZ","Product Two (DGT6704)",54,2003-01-13 00:00:00
"AAA","Product Two (DGT6704)",1000,2003-08-30 00:00:00
"BBB","Product Two (DGT6704)",45.5,2003-07-22 00:00:00
"BBB","Product Two (DGT6704)",46.1,2003-08-04 00:00:00
"BBB","Product Two (DGT6704)",46.1,2003-08-16 00:00:00
"BBB","Product Two (DGT6704)",44.75,2003-08-27 00:00:00
"CCC","Product Two (DGT6704)",1000,2003-08-30 00:00:00
"DDD","Product Two (DGT6704)",46.25,2003-05-08 00:00:00
"EEE","Product Two (DGT6704)",1000,2003-08-30 00:00:00
"FFF","Product Two (DGT6704)",1000,2003-08-30 00:00:00
"GGG","Product Two (DGT6704)",1000,2003-09-01 00:00:00
"HHH","Product Two (DGT6704)",46.1,2003-08-04 00:00:00
"III","Product Two (DGT6704)",1000,2003-01-13 00:00:00
"JJJ","Product Two (DGT6704)",47.45,2003-08-04 00:00:00
"JJJ","Product Two (DGT6704)",47.45,2003-09-01 00:00:00
"KKK","Product Two (DGT6704)",44.75,2003-07-14 00:00:00
"ZZZ","Product Three (QAT6785)",52,2003-01-13 00:00:00
"AAA","Product Three (QAT6785)",1000,2003-08-30 00:00:00
"BBB","Product Three (QAT6785)",45.5,2003-07-22 00:00:00
"BBB","Product Three (QAT6785)",532.25,2003-07-29 00:00:00
"BBB","Product Three (QAT6785)",1000,2003-07-30 00:00:00
"BBB","Product Three (QAT6785)",1000,2003-08-04 00:00:00
"BBB","Product Three (QAT6785)",46.1,2003-08-16 00:00:00
"BBB","Product Three (QAT6785)",44.75,2003-08-27 00:00:00
"CCC","Product Three (QAT6785)",42.65,2003-08-31 00:00:00
"DDD","Product Three (QAT6785)",46.25,2003-05-08 00:00:00
"EEE","Product Three (QAT6785)",1000,2003-08-30 00:00:00
"FFF","Product Three (QAT6785)",1000,2003-08-30 00:00:00
"GGG","Product Three (QAT6785)",1000,2003-09-01 00:00:00
"HHH","Product Three (QAT6785)",46.1,2003-08-04 00:00:00
"III","Product Three (QAT6785)",1000,2003-01-13 00:00:00
"JJJ","Product Three (QAT6785)",40.45,2003-08-04 00:00:00
"JJJ","Product Three (QAT6785)",40.45,2003-09-01 00:00:00
"KKK","Product Three (QAT6785)",44.75,2003-07-14 00:00:00
"ZZZ","Product Three (QAT556)",50.23,2003-01-13 00:00:00
"AAA","Product Three (QAT556)",1000,2003-08-30 00:00:00
"BBB","Product Three (QAT556)",44.75,2003-07-22 00:00:00
"BBB","Product Three (QAT556)",532.25,2003-07-29 00:00:00
"BBB","Product Three (QAT556)",1000,2003-07-30 00:00:00
"BBB","Product Three (QAT556)",1000,2003-08-03 00:00:00
"BBB","Product Three (QAT556)",1000,2003-08-04 00:00:00
"BBB","Product Three (QAT556)",44.75,2003-08-16 00:00:00
"BBB","Product Three (QAT556)",44.75,2003-08-27 00:00:00
"CCC","Product Three (QAT556)",1000,2003-08-30 00:00:00
"DDD","Product Three (QAT556)",46.25,2003-05-08 00:00:00
"EEE","Product Three (QAT556)",1000,2003-08-30 00:00:00
"FFF","Product Three (QAT556)",1000,2003-08-30 00:00:00
"GGG","Product Three (QAT556)",1000,2003-09-01 00:00:00
"HHH","Product Three (QAT556)",46.1,2003-08-04 00:00:00
"III","Product Three (QAT556)",1000,2003-01-13 00:00:00
"JJJ","Product Three (QAT556)",40.45,2003-08-04 00:00:00
"JJJ","Product Three (QAT556)",40.45,2003-09-01 00:00:00
"KKK","Product Three (QAT556)",44.75,2003-07-14 00:00:00
"JJJ","Product Three (QAT556)",40.15,2003-08-01 00:00:00

Jul 20 '05 #2

P: n/a
"netpurpose" <ne********@hotmail.com> wrote in message
news:31**************************@posting.google.c om...
Hi Jag,

Thank you for your response. I tried the query, but it gives me a
different pricing result:

ProductName Price
---------------------------------------- ---------------------
Product One (MXT234) 28.1500
Product Two (DGT6789) 44.3500
Product Three (QAT556) 40.1500

The correct result should be:

ProductName Price
---------------------------------------- ---------------------
Product One 33.5000
Product Two 44.7500
Product Three 40.4500

The reason is because for Product One, Manufacturer "BBB" has a price
of 28.15 on 2003-07-30, this price is no longer valid because "BBB"
has more recent price of 33.5 starting on 2003-08-27. Same case with
Product Two and Three (manufacturer "JJJ" overrides the 40.15 on
2003-08-01 with 40.45 on 2003-08-04).

I have to take the most recent prices from each manufacturer for a
particular product (price at the latest date as of today), and then
take the minimum price from the result.

Again, thank you for your help. Sorry I might not explain it well in
the beginning. Any further help is appreciated. Thank you very much
in advance!

Regards,
Netpurpose
I was a little too quick on the draw and misread your requirements.

SELECT ProductName, MIN(Price)
FROM (SELECT P1.Distributor,
SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) AS
ProductName,
P1.EffectiveDate AS LatestDate,
P1.price
FROM ProductList AS P1
LEFT OUTER JOIN
ProductList AS P2
ON P1.Distributor = P2.Distributor AND
P1.ProductName = P2.ProductName AND
P1.EffectiveDate <= CURRENT_TIMESTAMP AND
P2.EffectiveDate <= CURRENT_TIMESTAMP AND
P2.EffectiveDate > P1.EffectiveDate
WHERE P2.EffectiveDate IS NULL) AS LatestPrices
GROUP BY ProductName

Regards,
jag
"John Gilson" <ja*@acm.org> wrote in message news:<_u*********************@twister.nyc.rr.com>. ..
"netpurpose" <ne********@hotmail.com> wrote in message
news:31**************************@posting.google.c om...
I need to extract data from this table to find the lowest prices of
each product as of today. The product will be listed/grouped by the
name only, discarding the product code - I use SUBSTRING(ProductName,
1, CHARINDEX('(', ProductName)-2).

I can get this result, but I had to use several views (totally
inefficient). I think this can be done in one efficient/fast query,
but I can't think of one.

In the case that one query is not possible, is there other efficient
way to get the results? There are about 300K records in the table.

Any help is appreciated! Thanks a lot in advance!

Thanks,
Netpurpose


SELECT P1.ProductName, P1.Price
FROM ProductList AS P1
WHERE EffectiveDate <= CURRENT_TIMESTAMP AND
NOT EXISTS
(SELECT *
FROM ProductList AS P2
WHERE SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) =
SUBSTRING(P2.ProductName, 1,
CHARINDEX('(', P2.ProductName) - 2) AND
P2.EffectiveDate <= CURRENT_TIMESTAMP AND
P2.Price < P1.Price)

Regards,
jag

-----------------------START TABLE INFO-------------------------

Here is the desired result (on 8/29/03):

ProductName Price
---------------------------------------- ---------------------
Product One 33.5000
Product Three 40.4500
Product Two 44.7500
Here is the table info:

CREATE TABLE [ProductList] (
[Distributor] [nvarchar] (5) NULL ,
[ProductName] [nvarchar] (40) NULL ,
[Price] [money] NULL ,
[EffectiveDate] [smalldatetime] NULL
) ON [PRIMARY]
Table Data (comma delimited):
*Sorry I can't list in insert commands as there are too many.

"Manufacturer","ProductName","Price","EffectiveDat e"
"AAA","Product One (MXT234)",1000,2003-08-30 00:00:00
"BBB","Product One (MXT234)",1000,2003-07-29 00:00:00
"BBB","Product One (MXT234)",28.15,2003-07-30 00:00:00
"BBB","Product One (MXT234)",35.22,2003-08-04 00:00:00
"BBB","Product One (MXT234)",35.22,2003-08-04 00:00:00
"BBB","Product One (MXT234)",1000,2003-08-16 00:00:00
"BBB","Product One (MXT234)",33.8,2003-08-27 00:00:00
"CCC","Product One (MXT234)",33.25,2003-08-31 00:00:00
"DDD","Product One (MXT234)",46.25,2003-01-02 00:00:00
"EEE","Product One (MXT234)",1000,2003-08-30 00:00:00
"FFF","Product One (MXT234)",1000,2003-08-30 00:00:00
"GGG","Product One (MXT234)",1000,2003-09-01 00:00:00
"HHH","Product One (MXT234)",33.8,2003-08-04 00:00:00
"III","Product One (MXT234)",1000,2003-01-13 00:00:00
"JJJ","Product One (MXT234)",34.35,2003-07-30 00:00:00
"JJJ","Product One (MXT234)",34.35,2003-09-01 00:00:00
"KKK","Product One (MXT234)",1000,2003-08-30 00:00:00
"ZZZ","Product One (MXT205)",54,2003-01-13 00:00:00
"AAA","Product One (MXT205)",1000,2003-08-30 00:00:00
"BBB","Product One (MXT205)",33.95,2003-07-27 00:00:00
"BBB","Product One (MXT205)",33.95,2003-07-29 00:00:00
"BBB","Product One (MXT205)",35.22,2003-08-04 00:00:00
"BBB","Product One (MXT205)",33.8,2003-08-16 00:00:00
"BBB","Product One (MXT205)",33.5,2003-08-27 00:00:00
"CCC","Product One (MXT205)",1000,2003-08-30 00:00:00
"DDD","Product One (MXT205)",46.25,2003-01-02 00:00:00
"EEE","Product One (MXT205)",1000,2003-08-30 00:00:00
"FFF","Product One (MXT205)",1000,2003-08-30 00:00:00
"GGG","Product One (MXT205)",1000,2003-09-01 00:00:00
"HHH","Product One (MXT205)",33.95,2003-08-04 00:00:00
"III","Product One (MXT205)",1000,2003-01-13 00:00:00
"JJJ","Product One (MXT205)",34.35,2003-07-30 00:00:00
"JJJ","Product One (MXT205)",34.35,2003-09-01 00:00:00
"KKK","Product One (MXT205)",1000,2003-08-30 00:00:00
"ZZZ","Product One (MXT548)",54,2003-01-13 00:00:00
"AAA","Product One (MXT548)",25.04,2003-08-31 00:00:00
"BBB","Product One (MXT548)",33.95,2003-07-22 00:00:00
"BBB","Product One (MXT548)",33.95,2003-07-27 00:00:00
"BBB","Product One (MXT548)",35.22,2003-08-04 00:00:00
"BBB","Product One (MXT548)",33.8,2003-08-16 00:00:00
"BBB","Product One (MXT548)",33.8,2003-08-27 00:00:00
"CCC","Product One (MXT548)",1000,2003-08-30 00:00:00
"DDD","Product One (MXT548)",46.25,2003-01-02 00:00:00
"EEE","Product One (MXT548)",1000,2003-08-30 00:00:00
"FFF","Product One (MXT548)",1000,2003-08-30 00:00:00
"GGG","Product One (MXT548)",1000,2003-09-01 00:00:00
"HHH","Product One (MXT548)",33.8,2003-08-04 00:00:00
"III","Product One (MXT548)",1000,2003-01-13 00:00:00
"JJJ","Product One (MXT548)",34.35,2003-07-30 00:00:00
"JJJ","Product One (MXT548)",34.35,2003-09-01 00:00:00
"KKK","Product One (MXT548)",1000,2003-08-30 00:00:00
"ZZZ","Product Two (DGT6789)",54,2003-01-13 00:00:00
"AAA","Product Two (DGT6789)",1000,2003-08-30 00:00:00
"BBB","Product Two (DGT6789)",1000,2003-07-22 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-07-27 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-07-29 00:00:00
"BBB","Product Two (DGT6789)",44.35,2003-07-30 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-08-04 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-08-04 00:00:00
"BBB","Product Two (DGT6789)",1000,2003-08-23 00:00:00
"BBB","Product Two (DGT6789)",44.75,2003-08-27 00:00:00
"CCC","Product Two (DGT6789)",1000,2003-08-30 00:00:00
"DDD","Product Two (DGT6789)",46.25,2003-05-08 00:00:00
"EEE","Product Two (DGT6789)",1000,2003-08-30 00:00:00
"FFF","Product Two (DGT6789)",1000,2003-08-30 00:00:00
"GGG","Product Two (DGT6789)",1000,2003-09-01 00:00:00
"HHH","Product Two (DGT6789)",46.1,2003-08-04 00:00:00
"III","Product Two (DGT6789)",1000,2003-01-13 00:00:00
"JJJ","Product Two (DGT6789)",47.45,2003-08-04 00:00:00
"JJJ","Product Two (DGT6789)",47.45,2003-09-01 00:00:00
"KKK","Product Two (DGT6789)",44.75,2003-07-14 00:00:00
"ZZZ","Product Two (DGT6704)",54,2003-01-13 00:00:00
"AAA","Product Two (DGT6704)",1000,2003-08-30 00:00:00
"BBB","Product Two (DGT6704)",45.5,2003-07-22 00:00:00
"BBB","Product Two (DGT6704)",46.1,2003-08-04 00:00:00
"BBB","Product Two (DGT6704)",46.1,2003-08-16 00:00:00
"BBB","Product Two (DGT6704)",44.75,2003-08-27 00:00:00
"CCC","Product Two (DGT6704)",1000,2003-08-30 00:00:00
"DDD","Product Two (DGT6704)",46.25,2003-05-08 00:00:00
"EEE","Product Two (DGT6704)",1000,2003-08-30 00:00:00
"FFF","Product Two (DGT6704)",1000,2003-08-30 00:00:00
"GGG","Product Two (DGT6704)",1000,2003-09-01 00:00:00
"HHH","Product Two (DGT6704)",46.1,2003-08-04 00:00:00
"III","Product Two (DGT6704)",1000,2003-01-13 00:00:00
"JJJ","Product Two (DGT6704)",47.45,2003-08-04 00:00:00
"JJJ","Product Two (DGT6704)",47.45,2003-09-01 00:00:00
"KKK","Product Two (DGT6704)",44.75,2003-07-14 00:00:00
"ZZZ","Product Three (QAT6785)",52,2003-01-13 00:00:00
"AAA","Product Three (QAT6785)",1000,2003-08-30 00:00:00
"BBB","Product Three (QAT6785)",45.5,2003-07-22 00:00:00
"BBB","Product Three (QAT6785)",532.25,2003-07-29 00:00:00
"BBB","Product Three (QAT6785)",1000,2003-07-30 00:00:00
"BBB","Product Three (QAT6785)",1000,2003-08-04 00:00:00
"BBB","Product Three (QAT6785)",46.1,2003-08-16 00:00:00
"BBB","Product Three (QAT6785)",44.75,2003-08-27 00:00:00
"CCC","Product Three (QAT6785)",42.65,2003-08-31 00:00:00
"DDD","Product Three (QAT6785)",46.25,2003-05-08 00:00:00
"EEE","Product Three (QAT6785)",1000,2003-08-30 00:00:00
"FFF","Product Three (QAT6785)",1000,2003-08-30 00:00:00
"GGG","Product Three (QAT6785)",1000,2003-09-01 00:00:00
"HHH","Product Three (QAT6785)",46.1,2003-08-04 00:00:00
"III","Product Three (QAT6785)",1000,2003-01-13 00:00:00
"JJJ","Product Three (QAT6785)",40.45,2003-08-04 00:00:00
"JJJ","Product Three (QAT6785)",40.45,2003-09-01 00:00:00
"KKK","Product Three (QAT6785)",44.75,2003-07-14 00:00:00
"ZZZ","Product Three (QAT556)",50.23,2003-01-13 00:00:00
"AAA","Product Three (QAT556)",1000,2003-08-30 00:00:00
"BBB","Product Three (QAT556)",44.75,2003-07-22 00:00:00
"BBB","Product Three (QAT556)",532.25,2003-07-29 00:00:00
"BBB","Product Three (QAT556)",1000,2003-07-30 00:00:00
"BBB","Product Three (QAT556)",1000,2003-08-03 00:00:00
"BBB","Product Three (QAT556)",1000,2003-08-04 00:00:00
"BBB","Product Three (QAT556)",44.75,2003-08-16 00:00:00
"BBB","Product Three (QAT556)",44.75,2003-08-27 00:00:00
"CCC","Product Three (QAT556)",1000,2003-08-30 00:00:00
"DDD","Product Three (QAT556)",46.25,2003-05-08 00:00:00
"EEE","Product Three (QAT556)",1000,2003-08-30 00:00:00
"FFF","Product Three (QAT556)",1000,2003-08-30 00:00:00
"GGG","Product Three (QAT556)",1000,2003-09-01 00:00:00
"HHH","Product Three (QAT556)",46.1,2003-08-04 00:00:00
"III","Product Three (QAT556)",1000,2003-01-13 00:00:00
"JJJ","Product Three (QAT556)",40.45,2003-08-04 00:00:00
"JJJ","Product Three (QAT556)",40.45,2003-09-01 00:00:00
"KKK","Product Three (QAT556)",44.75,2003-07-14 00:00:00
"JJJ","Product Three (QAT556)",40.15,2003-08-01 00:00:00

Jul 20 '05 #3

P: n/a
Did I miscopy John's query? It gives me the future price of $25.04
for Product One, but is easy to fix by adding

AND P1.EffectiveDate <= CURRENT_TIMESTAMP

to the where clause of the derived table LatestPrices

John's initial idea of NOT EXISTS still works, too, in part. (Note
that I blew off the ProductName parsing by taking a hatchet to that
column with an update...
-- Be lazy
UPDATE ProductList SET
ProductName =
SUBSTRING(ProductName, 1,CHARINDEX('(', ProductName) - 2)
GO

-- For each product, select the lowest non-future
-- price that has not been superseded.
SELECT ProductName, MIN(Price) as Price -- get the lowest price
FROM (
SELECT ProductName, Price -- from all non-future prices
FROM ProductList P1
WHERE P1.EffectiveDate <= CURRENT_TIMESTAMP
AND NOT EXISTS ( -- that have not been superseded
SELECT * FROM ProductList P2
WHERE P2.Distributor = P1.Distributor
AND P2.ProductName = P1.ProductName
AND P2.EffectiveDate <= CURRENT_TIMESTAMP
AND P2.EffectiveDate > P1.EffectiveDate
)
) T
GROUP BY ProductName -- for each product
go

By the way, the delimited data was no trouble. I pasted it into
Excel, did Text To Columns, named the data region, and inserted it with:

insert into [ProductList]
select Manufacturer, ProductName, Price, EffectiveDate
from OpenRowset(
'Microsoft.Jet.OLEDB.4.0',
'Excel 8.0;Database=e:\excel\ProductList.xls',
'select * from ProductList')

Be sure to close the Excel file before inserting.

-- Steve Kass
-- Drew University
-- Ref: 2498EA13-1756-4C81-9307-25AFD5BB451D

netpurpose wrote:
Hi Jag,

Thanks a lot!! It works like a charm! Your query saves me a lot of headache.

I have struggled with this for quite a while now and I am glad I find help here.

Again, thank you very much! I really appreciate your help in such a short time!

Regards,
Netpurpose
"John Gilson" <ja*@acm.org> wrote in message news:<am*********************@twister.nyc.rr.com>. ..
"netpurpose" <ne********@hotmail.com> wrote in message
news:31**************************@posting.google .com...
Hi Jag,

Thank you for your response. I tried the query, but it gives me a
different pricing result:

ProductName Price
---------------------------------------- ---------------------
Product One (MXT234) 28.1500
Product Two (DGT6789) 44.3500
Product Three (QAT556) 40.1500

The correct result should be:

ProductName Price
---------------------------------------- ---------------------
Product One 33.5000
Product Two 44.7500
Product Three 40.4500

The reason is because for Product One, Manufacturer "BBB" has a price
of 28.15 on 2003-07-30, this price is no longer valid because "BBB"
has more recent price of 33.5 starting on 2003-08-27. Same case with
Product Two and Three (manufacturer "JJJ" overrides the 40.15 on
2003-08-01 with 40.45 on 2003-08-04).

I have to take the most recent prices from each manufacturer for a
particular product (price at the latest date as of today), and then
take the minimum price from the result.

Again, thank you for your help. Sorry I might not explain it well in
the beginning. Any further help is appreciated. Thank you very much
in advance!

Regards,
Netpurpose


I was a little too quick on the draw and misread your requirements.

SELECT ProductName, MIN(Price)
FROM (SELECT P1.Distributor,
SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) AS
ProductName,
P1.EffectiveDate AS LatestDate,
P1.price
FROM ProductList AS P1
LEFT OUTER JOIN
ProductList AS P2
ON P1.Distributor = P2.Distributor AND
P1.ProductName = P2.ProductName AND
P1.EffectiveDate <= CURRENT_TIMESTAMP AND
P2.EffectiveDate <= CURRENT_TIMESTAMP AND
P2.EffectiveDate > P1.EffectiveDate
WHERE P2.EffectiveDate IS NULL) AS LatestPrices
GROUP BY ProductName

Regards,
jag

"John Gilson" <ja*@acm.org> wrote in message news:<_u*********************@twister.nyc.rr.com>. ..

"netpurpose" <ne********@hotmail.com> wrote in message
news:31**************************@posting.goog le.com...

>I need to extract data from this table to find the lowest prices of
>each product as of today. The product will be listed/grouped by the
>name only, discarding the product code - I use SUBSTRING(ProductName,
>1, CHARINDEX('(', ProductName)-2).
>
>I can get this result, but I had to use several views (totally
>inefficient). I think this can be done in one efficient/fast query,
>but I can't think of one.
>
>In the case that one query is not possible, is there other efficient
>way to get the results? There are about 300K records in the table.
>
>Any help is appreciated! Thanks a lot in advance!
>
>Thanks,
>Netpurpose

SELECT P1.ProductName, P1.Price
FROM ProductList AS P1
WHERE EffectiveDate <= CURRENT_TIMESTAMP AND
NOT EXISTS
(SELECT *
FROM ProductList AS P2
WHERE SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) =
SUBSTRING(P2.ProductName, 1,
CHARINDEX('(', P2.ProductName) - 2) AND
P2.EffectiveDate <= CURRENT_TIMESTAMP AND
P2.Price < P1.Price)

Regards,
jag
>-----------------------START TABLE INFO-------------------------
>
>Here is the desired result (on 8/29/03):
>
>ProductName Price
>---------------------------------------- ---------------------
>Product One 33.5000
>Product Three 40.4500
>Product Two 44.7500
>
>
>Here is the table info:
>
>CREATE TABLE [ProductList] (
>[Distributor] [nvarchar] (5) NULL ,
>[ProductName] [nvarchar] (40) NULL ,
>[Price] [money] NULL ,
>[EffectiveDate] [smalldatetime] NULL
>) ON [PRIMARY]
>
>
>Table Data (comma delimited):
>*Sorry I can't list in insert commands as there are too many.
>
>"Manufacturer","ProductName","Price","Effecti veDate"
>"AAA","Product One (MXT234)",1000,2003-08-30 00:00:00
>"BBB","Product One (MXT234)",1000,2003-07-29 00:00:00
>"BBB","Product One (MXT234)",28.15,2003-07-30 00:00:00
>"BBB","Product One (MXT234)",35.22,2003-08-04 00:00:00
>"BBB","Product One (MXT234)",35.22,2003-08-04 00:00:00
>"BBB","Product One (MXT234)",1000,2003-08-16 00:00:00
>"BBB","Product One (MXT234)",33.8,2003-08-27 00:00:00
>"CCC","Product One (MXT234)",33.25,2003-08-31 00:00:00
>"DDD","Product One (MXT234)",46.25,2003-01-02 00:00:00
>"EEE","Product One (MXT234)",1000,2003-08-30 00:00:00
>"FFF","Product One (MXT234)",1000,2003-08-30 00:00:00
>"GGG","Product One (MXT234)",1000,2003-09-01 00:00:00
>"HHH","Product One (MXT234)",33.8,2003-08-04 00:00:00
>"III","Product One (MXT234)",1000,2003-01-13 00:00:00
>"JJJ","Product One (MXT234)",34.35,2003-07-30 00:00:00
>"JJJ","Product One (MXT234)",34.35,2003-09-01 00:00:00
>"KKK","Product One (MXT234)",1000,2003-08-30 00:00:00
>"ZZZ","Product One (MXT205)",54,2003-01-13 00:00:00
>"AAA","Product One (MXT205)",1000,2003-08-30 00:00:00
>"BBB","Product One (MXT205)",33.95,2003-07-27 00:00:00
>"BBB","Product One (MXT205)",33.95,2003-07-29 00:00:00
>"BBB","Product One (MXT205)",35.22,2003-08-04 00:00:00
>"BBB","Product One (MXT205)",33.8,2003-08-16 00:00:00
>"BBB","Product One (MXT205)",33.5,2003-08-27 00:00:00
>"CCC","Product One (MXT205)",1000,2003-08-30 00:00:00
>"DDD","Product One (MXT205)",46.25,2003-01-02 00:00:00
>"EEE","Product One (MXT205)",1000,2003-08-30 00:00:00
>"FFF","Product One (MXT205)",1000,2003-08-30 00:00:00
>"GGG","Product One (MXT205)",1000,2003-09-01 00:00:00
>"HHH","Product One (MXT205)",33.95,2003-08-04 00:00:00
>"III","Product One (MXT205)",1000,2003-01-13 00:00:00
>"JJJ","Product One (MXT205)",34.35,2003-07-30 00:00:00
>"JJJ","Product One (MXT205)",34.35,2003-09-01 00:00:00
>"KKK","Product One (MXT205)",1000,2003-08-30 00:00:00
>"ZZZ","Product One (MXT548)",54,2003-01-13 00:00:00
>"AAA","Product One (MXT548)",25.04,2003-08-31 00:00:00
>"BBB","Product One (MXT548)",33.95,2003-07-22 00:00:00
>"BBB","Product One (MXT548)",33.95,2003-07-27 00:00:00
>"BBB","Product One (MXT548)",35.22,2003-08-04 00:00:00
>"BBB","Product One (MXT548)",33.8,2003-08-16 00:00:00
>"BBB","Product One (MXT548)",33.8,2003-08-27 00:00:00
>"CCC","Product One (MXT548)",1000,2003-08-30 00:00:00
>"DDD","Product One (MXT548)",46.25,2003-01-02 00:00:00
>"EEE","Product One (MXT548)",1000,2003-08-30 00:00:00
>"FFF","Product One (MXT548)",1000,2003-08-30 00:00:00
>"GGG","Product One (MXT548)",1000,2003-09-01 00:00:00
>"HHH","Product One (MXT548)",33.8,2003-08-04 00:00:00
>"III","Product One (MXT548)",1000,2003-01-13 00:00:00
>"JJJ","Product One (MXT548)",34.35,2003-07-30 00:00:00
>"JJJ","Product One (MXT548)",34.35,2003-09-01 00:00:00
>"KKK","Product One (MXT548)",1000,2003-08-30 00:00:00
>"ZZZ","Product Two (DGT6789)",54,2003-01-13 00:00:00
>"AAA","Product Two (DGT6789)",1000,2003-08-30 00:00:00
>"BBB","Product Two (DGT6789)",1000,2003-07-22 00:00:00
>"BBB","Product Two (DGT6789)",44.75,2003-07-27 00:00:00
>"BBB","Product Two (DGT6789)",44.75,2003-07-29 00:00:00
>"BBB","Product Two (DGT6789)",44.35,2003-07-30 00:00:00
>"BBB","Product Two (DGT6789)",44.75,2003-08-04 00:00:00
>"BBB","Product Two (DGT6789)",44.75,2003-08-04 00:00:00
>"BBB","Product Two (DGT6789)",1000,2003-08-23 00:00:00
>"BBB","Product Two (DGT6789)",44.75,2003-08-27 00:00:00
>"CCC","Product Two (DGT6789)",1000,2003-08-30 00:00:00
>"DDD","Product Two (DGT6789)",46.25,2003-05-08 00:00:00
>"EEE","Product Two (DGT6789)",1000,2003-08-30 00:00:00
>"FFF","Product Two (DGT6789)",1000,2003-08-30 00:00:00
>"GGG","Product Two (DGT6789)",1000,2003-09-01 00:00:00
>"HHH","Product Two (DGT6789)",46.1,2003-08-04 00:00:00
>"III","Product Two (DGT6789)",1000,2003-01-13 00:00:00
>"JJJ","Product Two (DGT6789)",47.45,2003-08-04 00:00:00
>"JJJ","Product Two (DGT6789)",47.45,2003-09-01 00:00:00
>"KKK","Product Two (DGT6789)",44.75,2003-07-14 00:00:00
>"ZZZ","Product Two (DGT6704)",54,2003-01-13 00:00:00
>"AAA","Product Two (DGT6704)",1000,2003-08-30 00:00:00
>"BBB","Product Two (DGT6704)",45.5,2003-07-22 00:00:00
>"BBB","Product Two (DGT6704)",46.1,2003-08-04 00:00:00
>"BBB","Product Two (DGT6704)",46.1,2003-08-16 00:00:00
>"BBB","Product Two (DGT6704)",44.75,2003-08-27 00:00:00
>"CCC","Product Two (DGT6704)",1000,2003-08-30 00:00:00
>"DDD","Product Two (DGT6704)",46.25,2003-05-08 00:00:00
>"EEE","Product Two (DGT6704)",1000,2003-08-30 00:00:00
>"FFF","Product Two (DGT6704)",1000,2003-08-30 00:00:00
>"GGG","Product Two (DGT6704)",1000,2003-09-01 00:00:00
>"HHH","Product Two (DGT6704)",46.1,2003-08-04 00:00:00
>"III","Product Two (DGT6704)",1000,2003-01-13 00:00:00
>"JJJ","Product Two (DGT6704)",47.45,2003-08-04 00:00:00
>"JJJ","Product Two (DGT6704)",47.45,2003-09-01 00:00:00
>"KKK","Product Two (DGT6704)",44.75,2003-07-14 00:00:00
>"ZZZ","Product Three (QAT6785)",52,2003-01-13 00:00:00
>"AAA","Product Three (QAT6785)",1000,2003-08-30 00:00:00
>"BBB","Product Three (QAT6785)",45.5,2003-07-22 00:00:00
>"BBB","Product Three (QAT6785)",532.25,2003-07-29 00:00:00
>"BBB","Product Three (QAT6785)",1000,2003-07-30 00:00:00
>"BBB","Product Three (QAT6785)",1000,2003-08-04 00:00:00
>"BBB","Product Three (QAT6785)",46.1,2003-08-16 00:00:00
>"BBB","Product Three (QAT6785)",44.75,2003-08-27 00:00:00
>"CCC","Product Three (QAT6785)",42.65,2003-08-31 00:00:00
>"DDD","Product Three (QAT6785)",46.25,2003-05-08 00:00:00
>"EEE","Product Three (QAT6785)",1000,2003-08-30 00:00:00
>"FFF","Product Three (QAT6785)",1000,2003-08-30 00:00:00
>"GGG","Product Three (QAT6785)",1000,2003-09-01 00:00:00
>"HHH","Product Three (QAT6785)",46.1,2003-08-04 00:00:00
>"III","Product Three (QAT6785)",1000,2003-01-13 00:00:00
>"JJJ","Product Three (QAT6785)",40.45,2003-08-04 00:00:00
>"JJJ","Product Three (QAT6785)",40.45,2003-09-01 00:00:00
>"KKK","Product Three (QAT6785)",44.75,2003-07-14 00:00:00
>"ZZZ","Product Three (QAT556)",50.23,2003-01-13 00:00:00
>"AAA","Product Three (QAT556)",1000,2003-08-30 00:00:00
>"BBB","Product Three (QAT556)",44.75,2003-07-22 00:00:00
>"BBB","Product Three (QAT556)",532.25,2003-07-29 00:00:00
>"BBB","Product Three (QAT556)",1000,2003-07-30 00:00:00
>"BBB","Product Three (QAT556)",1000,2003-08-03 00:00:00
>"BBB","Product Three (QAT556)",1000,2003-08-04 00:00:00
>"BBB","Product Three (QAT556)",44.75,2003-08-16 00:00:00
>"BBB","Product Three (QAT556)",44.75,2003-08-27 00:00:00
>"CCC","Product Three (QAT556)",1000,2003-08-30 00:00:00
>"DDD","Product Three (QAT556)",46.25,2003-05-08 00:00:00
>"EEE","Product Three (QAT556)",1000,2003-08-30 00:00:00
>"FFF","Product Three (QAT556)",1000,2003-08-30 00:00:00
>"GGG","Product Three (QAT556)",1000,2003-09-01 00:00:00
>"HHH","Product Three (QAT556)",46.1,2003-08-04 00:00:00
>"III","Product Three (QAT556)",1000,2003-01-13 00:00:00
>"JJJ","Product Three (QAT556)",40.45,2003-08-04 00:00:00
>"JJJ","Product Three (QAT556)",40.45,2003-09-01 00:00:00
>"KKK","Product Three (QAT556)",44.75,2003-07-14 00:00:00
>"JJJ","Product Three (QAT556)",40.15,2003-08-01 00:00:00


Jul 20 '05 #4

P: n/a
Hi Steve,

Thanks for your response. When I copied John's query, it works fine
and gives me the correct results. I did run both your query and his
against 330K of records, and it seems that his query runs much faster
(more than 10 times faster). I ran your query against clean products
names without the codes.

I am too novice to even know why the big difference. Both query
yields the same results. Can you tell why his statement is much more
efficient? LEFT OUTER JOIN vs EXISTS? I do want to learn from this.

Also, thanks for showing me the command to import the excel file to
db. Good to know :)

Thanks,
Netpurpose

Steve Kass <sk***@drew.edu> wrote in message news:<xW*****************@newsread2.news.atl.earth link.net>...
Did I miscopy John's query? It gives me the future price of $25.04
for Product One, but is easy to fix by adding

AND P1.EffectiveDate <= CURRENT_TIMESTAMP

to the where clause of the derived table LatestPrices

John's initial idea of NOT EXISTS still works, too, in part. (Note
that I blew off the ProductName parsing by taking a hatchet to that
column with an update...
-- Be lazy
UPDATE ProductList SET
ProductName =
SUBSTRING(ProductName, 1,CHARINDEX('(', ProductName) - 2)
GO

-- For each product, select the lowest non-future
-- price that has not been superseded.
SELECT ProductName, MIN(Price) as Price -- get the lowest price
FROM (
SELECT ProductName, Price -- from all non-future prices
FROM ProductList P1
WHERE P1.EffectiveDate <= CURRENT_TIMESTAMP
AND NOT EXISTS ( -- that have not been superseded
SELECT * FROM ProductList P2
WHERE P2.Distributor = P1.Distributor
AND P2.ProductName = P1.ProductName
AND P2.EffectiveDate <= CURRENT_TIMESTAMP
AND P2.EffectiveDate > P1.EffectiveDate
)
) T
GROUP BY ProductName -- for each product
go

By the way, the delimited data was no trouble. I pasted it into
Excel, did Text To Columns, named the data region, and inserted it with:

insert into [ProductList]
select Manufacturer, ProductName, Price, EffectiveDate
from OpenRowset(
'Microsoft.Jet.OLEDB.4.0',
'Excel 8.0;Database=e:\excel\ProductList.xls',
'select * from ProductList')

Be sure to close the Excel file before inserting.

-- Steve Kass
-- Drew University
-- Ref: 2498EA13-1756-4C81-9307-25AFD5BB451D

netpurpose wrote:
Hi Jag,

Thanks a lot!! It works like a charm! Your query saves me a lot of headache.

I have struggled with this for quite a while now and I am glad I find help here.

Again, thank you very much! I really appreciate your help in such a short time!

Regards,
Netpurpose
"John Gilson" <ja*@acm.org> wrote in message news:<am*********************@twister.nyc.rr.com>. ..
"netpurpose" <ne********@hotmail.com> wrote in message
news:31**************************@posting.google .com...

Hi Jag,

Thank you for your response. I tried the query, but it gives me a
different pricing result:

ProductName Price
---------------------------------------- ---------------------
Product One (MXT234) 28.1500
Product Two (DGT6789) 44.3500
Product Three (QAT556) 40.1500

The correct result should be:

ProductName Price
---------------------------------------- ---------------------
Product One 33.5000
Product Two 44.7500
Product Three 40.4500

The reason is because for Product One, Manufacturer "BBB" has a price
of 28.15 on 2003-07-30, this price is no longer valid because "BBB"
has more recent price of 33.5 starting on 2003-08-27. Same case with
Product Two and Three (manufacturer "JJJ" overrides the 40.15 on
2003-08-01 with 40.45 on 2003-08-04).

I have to take the most recent prices from each manufacturer for a
particular product (price at the latest date as of today), and then
take the minimum price from the result.

Again, thank you for your help. Sorry I might not explain it well in
the beginning. Any further help is appreciated. Thank you very much
in advance!

Regards,
Netpurpose

I was a little too quick on the draw and misread your requirements.

SELECT ProductName, MIN(Price)
FROM (SELECT P1.Distributor,
SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) AS
ProductName,
P1.EffectiveDate AS LatestDate,
P1.price
FROM ProductList AS P1
LEFT OUTER JOIN
ProductList AS P2
ON P1.Distributor = P2.Distributor AND
P1.ProductName = P2.ProductName AND
P1.EffectiveDate <= CURRENT_TIMESTAMP AND
P2.EffectiveDate <= CURRENT_TIMESTAMP AND
P2.EffectiveDate > P1.EffectiveDate
WHERE P2.EffectiveDate IS NULL) AS LatestPrices
GROUP BY ProductName

Regards,
jag
"John Gilson" <ja*@acm.org> wrote in message news:<_u*********************@twister.nyc.rr.com>. ..

>"netpurpose" <ne********@hotmail.com> wrote in message
>news:31**************************@posting.goog le.com...
>
>>I need to extract data from this table to find the lowest prices of
>>each product as of today. The product will be listed/grouped by the
>>name only, discarding the product code - I use SUBSTRING(ProductName,
>>1, CHARINDEX('(', ProductName)-2).
>>
>>I can get this result, but I had to use several views (totally
>>inefficient). I think this can be done in one efficient/fast query,
>>but I can't think of one.
>>
>>In the case that one query is not possible, is there other efficient
>>way to get the results? There are about 300K records in the table.
>>
>>Any help is appreciated! Thanks a lot in advance!
>>
>>Thanks,
>>Netpurpose
>
>SELECT P1.ProductName, P1.Price
>FROM ProductList AS P1
>WHERE EffectiveDate <= CURRENT_TIMESTAMP AND
> NOT EXISTS
> (SELECT *
> FROM ProductList AS P2
> WHERE SUBSTRING(P1.ProductName, 1,
> CHARINDEX('(', P1.ProductName) - 2) =
> SUBSTRING(P2.ProductName, 1,
> CHARINDEX('(', P2.ProductName) - 2) AND
> P2.EffectiveDate <= CURRENT_TIMESTAMP AND
> P2.Price < P1.Price)
>
>Regards,
>jag
>
>

Jul 20 '05 #5

P: n/a
When I ran John's query on your sample data, It
returned the price of $25.04 for Product One, a price
that was not effective on the day I ran the query.

Make sure your sample data has some examples where
the lowest price is a future price that has been
recorded but is not yet effective.

As far as efficiency goes, all I did was look at query
plans. What I found was that John's query and mine
had virtually identical plans.

What I did was this:

Removed the part of product name in parentheses. If that data
is important, it should be a separate column. I removed it,
since to make this efficient there needed (I think) to be an
index with the ProductName value you want in the output, without
the extra comment, as the first column.

Removed all cases where the same (ProductName, Distributor,
EffectiveDate) appeared in more than one row (these probably
appeared when I removed the extra part of the product name).

Declared (ProductName, Distributor, EffectiveDate) to be the
primary key. Maybe I missed something and this does not work
as a key, but it seemed like a good choice for an index to
make the query fast. If it's not a key, add price as
a fourth column.

I realized now that there was extra nesting in my query.
I don't think it should have slowed it down tenfold, but the
outer two selects can be combined (if the data has no duplicates
in my key columns).
-- Select the lowest price
SELECT ProductName, MIN(Price)

-- from the table
FROM ProductList P1

-- that is not a future price
WHERE P1.EffectiveDate <= CURRENT_TIMESTAMP

-- and that has not been superseded
AND NOT EXISTS (
-- by another price
SELECT * FROM ProductList P2
-- from the same distributor
WHERE P2.Distributor = P1.Distributor
-- for the same product
AND P2.ProductName = P1.ProductName
-- which other price has gone into effect
AND P2.EffectiveDate <= CURRENT_TIMESTAMP
-- more recently
AND P2.EffectiveDate > P1.EffectiveDate
)

-- for each product
GROUP BY ProductName

Steve
netpurpose wrote:
Hi Steve,

Thanks for your response. When I copied John's query, it works fine
and gives me the correct results. I did run both your query and his
against 330K of records, and it seems that his query runs much faster
(more than 10 times faster). I ran your query against clean products
names without the codes.

I am too novice to even know why the big difference. Both query
yields the same results. Can you tell why his statement is much more
efficient? LEFT OUTER JOIN vs EXISTS? I do want to learn from this.

Also, thanks for showing me the command to import the excel file to
db. Good to know :)

Thanks,
Netpurpose

Steve Kass <sk***@drew.edu> wrote in message news:<xW*****************@newsread2.news.atl.earth link.net>...
Did I miscopy John's query? It gives me the future price of $25.04
for Product One, but is easy to fix by adding

AND P1.EffectiveDate <= CURRENT_TIMESTAMP

to the where clause of the derived table LatestPrices

John's initial idea of NOT EXISTS still works, too, in part. (Note
that I blew off the ProductName parsing by taking a hatchet to that
column with an update...
-- Be lazy
UPDATE ProductList SET
ProductName =
SUBSTRING(ProductName, 1,CHARINDEX('(', ProductName) - 2)
GO

-- For each product, select the lowest non-future
-- price that has not been superseded.
SELECT ProductName, MIN(Price) as Price -- get the lowest price
FROM (
SELECT ProductName, Price -- from all non-future prices
FROM ProductList P1
WHERE P1.EffectiveDate <= CURRENT_TIMESTAMP
AND NOT EXISTS ( -- that have not been superseded
SELECT * FROM ProductList P2
WHERE P2.Distributor = P1.Distributor
AND P2.ProductName = P1.ProductName
AND P2.EffectiveDate <= CURRENT_TIMESTAMP
AND P2.EffectiveDate > P1.EffectiveDate
)
) T
GROUP BY ProductName -- for each product
go

By the way, the delimited data was no trouble. I pasted it into
Excel, did Text To Columns, named the data region, and inserted it with:

insert into [ProductList]
select Manufacturer, ProductName, Price, EffectiveDate
from OpenRowset(
'Microsoft.Jet.OLEDB.4.0',
'Excel 8.0;Database=e:\excel\ProductList.xls',
'select * from ProductList')

Be sure to close the Excel file before inserting.

-- Steve Kass
-- Drew University
-- Ref: 2498EA13-1756-4C81-9307-25AFD5BB451D

netpurpose wrote:
Hi Jag,

Thanks a lot!! It works like a charm! Your query saves me a lot of headache.

I have struggled with this for quite a while now and I am glad I find help here.

Again, thank you very much! I really appreciate your help in such a short time!

Regards,
Netpurpose
"John Gilson" <ja*@acm.org> wrote in message news:<am*********************@twister.nyc.rr.com>. ..
"netpurpose" <ne********@hotmail.com> wrote in message
news:31**************************@posting.goog le.com...
>Hi Jag,
>
>Thank you for your response. I tried the query, but it gives me a
>different pricing result:
>
>ProductName Price
>---------------------------------------- ---------------------
>Product One (MXT234) 28.1500
>Product Two (DGT6789) 44.3500
>Product Three (QAT556) 40.1500
>
>The correct result should be:
>
>ProductName Price
>---------------------------------------- ---------------------
>Product One 33.5000
>Product Two 44.7500
>Product Three 40.4500
>
>The reason is because for Product One, Manufacturer "BBB" has a price
>of 28.15 on 2003-07-30, this price is no longer valid because "BBB"
>has more recent price of 33.5 starting on 2003-08-27. Same case with
>Product Two and Three (manufacturer "JJJ" overrides the 40.15 on
>2003-08-01 with 40.45 on 2003-08-04).
>
>I have to take the most recent prices from each manufacturer for a
>particular product (price at the latest date as of today), and then
>take the minimum price from the result.
>
>Again, thank you for your help. Sorry I might not explain it well in
>the beginning. Any further help is appreciated. Thank you very much
>in advance!
>
>Regards,
>Netpurpose

I was a little too quick on the draw and misread your requirements.

SELECT ProductName, MIN(Price)

FROM (SELECT P1.Distributor,

SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) AS
ProductName,
P1.EffectiveDate AS LatestDate,
P1.price
FROM ProductList AS P1
LEFT OUTER JOIN
ProductList AS P2
ON P1.Distributor = P2.Distributor AND
P1.ProductName = P2.ProductName AND
P1.EffectiveDate <= CURRENT_TIMESTAMP AND
P2.EffectiveDate <= CURRENT_TIMESTAMP AND
P2.EffectiveDate > P1.EffectiveDate
WHERE P2.EffectiveDate IS NULL) AS LatestPrices
GROUP BY ProductName

Regards,
jag

>"John Gilson" <ja*@acm.org> wrote in message news:<_u*********************@twister.nyc.rr.com>. ..
>
>
>>"netpurpose" <ne********@hotmail.com> wrote in message
>>news:31**************************@posting.go ogle.com...
>>
>>
>>>I need to extract data from this table to find the lowest prices of
>>>each product as of today. The product will be listed/grouped by the
>>>name only, discarding the product code - I use SUBSTRING(ProductName,
>>>1, CHARINDEX('(', ProductName)-2).
>>>
>>>I can get this result, but I had to use several views (totally
>>>inefficient). I think this can be done in one efficient/fast query,
>>>but I can't think of one.
>>>
>>>In the case that one query is not possible, is there other efficient
>>>way to get the results? There are about 300K records in the table.
>>>
>>>Any help is appreciated! Thanks a lot in advance!
>>>
>>>Thanks,
>>>Netpurpose
>>
>>SELECT P1.ProductName, P1.Price
>
>>FROM ProductList AS P1
>
>>WHERE EffectiveDate <= CURRENT_TIMESTAMP AND
>> NOT EXISTS
>> (SELECT *
>> FROM ProductList AS P2
>> WHERE SUBSTRING(P1.ProductName, 1,
>> CHARINDEX('(', P1.ProductName) - 2) =
>> SUBSTRING(P2.ProductName, 1,
>> CHARINDEX('(', P2.ProductName) - 2) AND
>> P2.EffectiveDate <= CURRENT_TIMESTAMP AND
>> P2.Price < P1.Price)
>>
>>Regards,
>>jag
>>
>>


Jul 20 '05 #6

P: n/a
Hi John and Steve,

Thank you very much for your help and the quick responses! I really
appreciate them.

Steve, thanks for explaining and commenting your query. I get a much
better understanding now.

John, I think in this last query, P2.EffectiveDate <=
CURRENT_TIMESTAMP is missing from the OUTER JOIN. But as you
mentioned, it works fine when I just take the previous query and move
out the P1.EffectiveDate <= CURRENT_TIMESTAMP. I didn't realize there
was a problem before because the live data as of yesterday has no
future pricing. Sorry, I should have tested it better.

Again, thanks to you both. The system works great and fast now!

Sincerely,
netpurpose
"John Gilson" <ja*@acm.org> wrote in message news:<Q5*********************@twister.nyc.rr.com>. ..
"Steve Kass" <sk***@drew.edu> wrote in message
news:u5*****************@newsread2.news.atl.earthl ink.net...
When I ran John's query on your sample data, It
returned the price of $25.04 for Product One, a price
that was not effective on the day I ran the query.

Make sure your sample data has some examples where
the lowest price is a future price that has been
recorded but is not yet effective.
Steve, you're absolutely right and stems from the (mis)placement
of the selection criteria for the outer join. The constraint
P1.EffectiveDate <= CURRENT_TIMESTAMP
should be applied *after* the outer join condition, that is, in the
WHERE clause. So this should do the right thing:

SELECT ProductName, MIN(Price)
FROM (SELECT P1.Distributor,
SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) AS
ProductName,
P1.EffectiveDate AS LatestDate,
P1.price
FROM ProductList AS P1
LEFT OUTER JOIN
ProductList AS P2
ON P1.Distributor = P2.Distributor AND
P1.ProductName = P2.ProductName AND

P2.EffectiveDate > P1.EffectiveDate
WHERE P2.EffectiveDate IS NULL AND
P1.EffectiveDate <= CURRENT_TIMESTAMP)
AS LatestPrices
GROUP BY ProductName

Regards,
jag
As far as efficiency goes, all I did was look at query
plans. What I found was that John's query and mine
had virtually identical plans.

What I did was this:

Removed the part of product name in parentheses. If that data
is important, it should be a separate column. I removed it,
since to make this efficient there needed (I think) to be an
index with the ProductName value you want in the output, without
the extra comment, as the first column.

Removed all cases where the same (ProductName, Distributor,
EffectiveDate) appeared in more than one row (these probably
appeared when I removed the extra part of the product name).

Declared (ProductName, Distributor, EffectiveDate) to be the
primary key. Maybe I missed something and this does not work
as a key, but it seemed like a good choice for an index to
make the query fast. If it's not a key, add price as
a fourth column.

I realized now that there was extra nesting in my query.
I don't think it should have slowed it down tenfold, but the
outer two selects can be combined (if the data has no duplicates
in my key columns).
-- Select the lowest price
SELECT ProductName, MIN(Price)

-- from the table
FROM ProductList P1

-- that is not a future price
WHERE P1.EffectiveDate <= CURRENT_TIMESTAMP

-- and that has not been superseded
AND NOT EXISTS (
-- by another price
SELECT * FROM ProductList P2
-- from the same distributor
WHERE P2.Distributor = P1.Distributor
-- for the same product
AND P2.ProductName = P1.ProductName
-- which other price has gone into effect
AND P2.EffectiveDate <= CURRENT_TIMESTAMP
-- more recently
AND P2.EffectiveDate > P1.EffectiveDate
)

-- for each product
GROUP BY ProductName

Steve
netpurpose wrote:
Hi Steve,

Thanks for your response. When I copied John's query, it works fine
and gives me the correct results. I did run both your query and his
against 330K of records, and it seems that his query runs much faster
(more than 10 times faster). I ran your query against clean products
names without the codes.

I am too novice to even know why the big difference. Both query
yields the same results. Can you tell why his statement is much more
efficient? LEFT OUTER JOIN vs EXISTS? I do want to learn from this.

Also, thanks for showing me the command to import the excel file to
db. Good to know :)

Thanks,
Netpurpose

Steve Kass <sk***@drew.edu> wrote in message news:<xW*****************@newsread2.news.atl.earth link.net>...
>Did I miscopy John's query? It gives me the future price of $25.04
>for Product One, but is easy to fix by adding
>
> AND P1.EffectiveDate <= CURRENT_TIMESTAMP
>
>to the where clause of the derived table LatestPrices
>
>John's initial idea of NOT EXISTS still works, too, in part. (Note
>that I blew off the ProductName parsing by taking a hatchet to that
>column with an update...
>
>
>-- Be lazy
>UPDATE ProductList SET
> ProductName =
> SUBSTRING(ProductName, 1,CHARINDEX('(', ProductName) - 2)
>GO
>
>-- For each product, select the lowest non-future
>-- price that has not been superseded.
>SELECT ProductName, MIN(Price) as Price -- get the lowest price
>FROM (
> SELECT ProductName, Price -- from all non-future prices
> FROM ProductList P1
> WHERE P1.EffectiveDate <= CURRENT_TIMESTAMP
> AND NOT EXISTS ( -- that have not been superseded
> SELECT * FROM ProductList P2
> WHERE P2.Distributor = P1.Distributor
> AND P2.ProductName = P1.ProductName
> AND P2.EffectiveDate <= CURRENT_TIMESTAMP
> AND P2.EffectiveDate > P1.EffectiveDate
> )
>) T
>GROUP BY ProductName -- for each product
>go
>
>By the way, the delimited data was no trouble. I pasted it into
>Excel, did Text To Columns, named the data region, and inserted it with:
>
>insert into [ProductList]
>select Manufacturer, ProductName, Price, EffectiveDate
>from OpenRowset(
> 'Microsoft.Jet.OLEDB.4.0',
> 'Excel 8.0;Database=e:\excel\ProductList.xls',
> 'select * from ProductList')
>
>Be sure to close the Excel file before inserting.
>
>-- Steve Kass
>-- Drew University
>-- Ref: 2498EA13-1756-4C81-9307-25AFD5BB451D
>
>
>
>netpurpose wrote:
>
>>Hi Jag,
>>
>>Thanks a lot!! It works like a charm! Your query saves me a lot of headache.
>>
>>I have struggled with this for quite a while now and I am glad I find help here.
>>
>>Again, thank you very much! I really appreciate your help in such a short time!
>>
>>Regards,
>>Netpurpose
>>
>>
>>"John Gilson" <ja*@acm.org> wrote in message news:<am*********************@twister.nyc.rr.com>. ..>>
>>
>>>"netpurpose" <ne********@hotmail.com> wrote in message
>>>news:31**************************@posting.goog le.com...
>>>
>>>
>>>>Hi Jag,
>>>>
>>>>Thank you for your response. I tried the query, but it gives me a
>>>>different pricing result:
>>>>
>>>>ProductName Price
>>>>---------------------------------------- ---------------------
>>>>Product One (MXT234) 28.1500
>>>>Product Two (DGT6789) 44.3500
>>>>Product Three (QAT556) 40.1500
>>>>
>>>>The correct result should be:
>>>>
>>>>ProductName Price
>>>>---------------------------------------- ---------------------
>>>>Product One 33.5000
>>>>Product Two 44.7500
>>>>Product Three 40.4500
>>>>
>>>>The reason is because for Product One, Manufacturer "BBB" has a price
>>>>of 28.15 on 2003-07-30, this price is no longer valid because "BBB"
>>>>has more recent price of 33.5 starting on 2003-08-27. Same case with
>>>>Product Two and Three (manufacturer "JJJ" overrides the 40.15 on
>>>>2003-08-01 with 40.45 on 2003-08-04).
>>>>
>>>>I have to take the most recent prices from each manufacturer for a
>>>>particular product (price at the latest date as of today), and then
>>>>take the minimum price from the result.
>>>>
>>>>Again, thank you for your help. Sorry I might not explain it well in
>>>>the beginning. Any further help is appreciated. Thank you very much
>>>>in advance!
>>>>
>>>>Regards,
>>>>Netpurpose
>>>
>>>I was a little too quick on the draw and misread your requirements.
>>>
>>>SELECT ProductName, MIN(Price)>FROM (SELECT P1.Distributor,> SUBSTRING(P1.ProductName, 1,
>>> CHARINDEX('(', P1.ProductName) - 2) AS
>>> ProductName,
>>> P1.EffectiveDate AS LatestDate,
>>> P1.price
>>> FROM ProductList AS P1
>>> LEFT OUTER JOIN
>>> ProductList AS P2
>>> ON P1.Distributor = P2.Distributor AND
>>> P1.ProductName = P2.ProductName AND
>>> P1.EffectiveDate <= CURRENT_TIMESTAMP AND
>>> P2.EffectiveDate <= CURRENT_TIMESTAMP AND
>>> P2.EffectiveDate > P1.EffectiveDate
>>> WHERE P2.EffectiveDate IS NULL) AS LatestPrices
>>>GROUP BY ProductName
>>>
>>>Regards,
>>>jag
>>>
>>>
>>>
>>>>"John Gilson" <ja*@acm.org> wrote in message news:<_u*********************@twister.nyc.rr.com>. ..>>>>
>>>>
>>>>>"netpurpose" <ne********@hotmail.com> wrote in message
>>>>>news:31**************************@posting.go ogle.com...
>>>>>
>>>>>
>>>>>>I need to extract data from this table to find the lowest prices of
>>>>>>each product as of today. The product will be listed/grouped by the
>>>>>>name only, discarding the product code - I use SUBSTRING(ProductName,
>>>>>>1, CHARINDEX('(', ProductName)-2).
>>>>>>
>>>>>>I can get this result, but I had to use several views (totally
>>>>>>inefficient). I think this can be done in one efficient/fast query,
>>>>>>but I can't think of one.
>>>>>>
>>>>>>In the case that one query is not possible, is there other efficient
>>>>>>way to get the results? There are about 300K records in the table.
>>>>>>
>>>>>>Any help is appreciated! Thanks a lot in advance!
>>>>>>
>>>>>>Thanks,
>>>>>>Netpurpose
>>>>>
>>>>>SELECT P1.ProductName, P1.Price>>>FROM ProductList AS P1>>>WHERE EffectiveDate <= CURRENT_TIMESTAMP AND
>>>>> NOT EXISTS
>>>>> (SELECT *
>>>>> FROM ProductList AS P2
>>>>> WHERE SUBSTRING(P1.ProductName, 1,
>>>>> CHARINDEX('(', P1.ProductName) - 2) =
>>>>> SUBSTRING(P2.ProductName, 1,
>>>>> CHARINDEX('(', P2.ProductName) - 2) AND>>>>> P2.EffectiveDate <= CURRENT_TIMESTAMP AND
>>>>> P2.Price < P1.Price)
>>>>>
>>>>>Regards,
>>>>>jag
>>>>>
>>>>>

Jul 20 '05 #7

P: n/a
John,

I hate to be a pest, but I believe you need the
date restriction in two places. The query here will
fail if the lowest price for a product comes from a
distributor that has already announced a price to become
effective in the future. If that is true, the future
price will come up on the right side of the join, since
there is no date restriction there. That makes the value
of P2.EffectiveDate not null and in the future, and the
P1.Price in that row, despite being the lowest for the
product, is filtered out.

Ok, I lied - I don't hate being a pest, but I do
think your query doesn't quite work.

Steve

John Gilson wrote:
"Steve Kass" <sk***@drew.edu> wrote in message
news:u5*****************@newsread2.news.atl.earthl ink.net...
When I ran John's query on your sample data, It
returned the price of $25.04 for Product One, a price
that was not effective on the day I ran the query.

Make sure your sample data has some examples where
the lowest price is a future price that has been
recorded but is not yet effective.

Steve, you're absolutely right and stems from the (mis)placement
of the selection criteria for the outer join. The constraint
P1.EffectiveDate <= CURRENT_TIMESTAMP
should be applied *after* the outer join condition, that is, in the
WHERE clause. So this should do the right thing:

SELECT ProductName, MIN(Price)
FROM (SELECT P1.Distributor,
SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) AS
ProductName,
P1.EffectiveDate AS LatestDate,
P1.price
FROM ProductList AS P1
LEFT OUTER JOIN
ProductList AS P2
ON P1.Distributor = P2.Distributor AND
P1.ProductName = P2.ProductName AND
P2.EffectiveDate > P1.EffectiveDate
WHERE P2.EffectiveDate IS NULL AND
P1.EffectiveDate <= CURRENT_TIMESTAMP)
AS LatestPrices
GROUP BY ProductName

Regards,
jag

As far as efficiency goes, all I did was look at query
plans. What I found was that John's query and mine
had virtually identical plans.

What I did was this:

Removed the part of product name in parentheses. If that data
is important, it should be a separate column. I removed it,
since to make this efficient there needed (I think) to be an
index with the ProductName value you want in the output, without
the extra comment, as the first column.

Removed all cases where the same (ProductName, Distributor,
EffectiveDate) appeared in more than one row (these probably
appeared when I removed the extra part of the product name).

Declared (ProductName, Distributor, EffectiveDate) to be the
primary key. Maybe I missed something and this does not work
as a key, but it seemed like a good choice for an index to
make the query fast. If it's not a key, add price as
a fourth column.

I realized now that there was extra nesting in my query.
I don't think it should have slowed it down tenfold, but the
outer two selects can be combined (if the data has no duplicates
in my key columns).
-- Select the lowest price
SELECT ProductName, MIN(Price)

-- from the table
FROM ProductList P1

-- that is not a future price
WHERE P1.EffectiveDate <= CURRENT_TIMESTAMP

-- and that has not been superseded
AND NOT EXISTS (
-- by another price
SELECT * FROM ProductList P2
-- from the same distributor
WHERE P2.Distributor = P1.Distributor
-- for the same product
AND P2.ProductName = P1.ProductName
-- which other price has gone into effect
AND P2.EffectiveDate <= CURRENT_TIMESTAMP
-- more recently
AND P2.EffectiveDate > P1.EffectiveDate
)

-- for each product
GROUP BY ProductName

Steve
netpurpose wrote:
Hi Steve,

Thanks for your response. When I copied John's query, it works fine
and gives me the correct results. I did run both your query and his
against 330K of records, and it seems that his query runs much faster
(more than 10 times faster). I ran your query against clean products
names without the codes.

I am too novice to even know why the big difference. Both query
yields the same results. Can you tell why his statement is much more
efficient? LEFT OUTER JOIN vs EXISTS? I do want to learn from this.

Also, thanks for showing me the command to import the excel file to
db. Good to know :)

Thanks,
Netpurpose

Steve Kass <sk***@drew.edu> wrote in message
news:<xW*****************@newsread2.news.atl.earth link.net>...
Did I miscopy John's query? It gives me the future price of $25.04
for Product One, but is easy to fix by adding

AND P1.EffectiveDate <= CURRENT_TIMESTAMP

to the where clause of the derived table LatestPrices

John's initial idea of NOT EXISTS still works, too, in part. (Note
that I blew off the ProductName parsing by taking a hatchet to that
column with an update...
-- Be lazy
UPDATE ProductList SET
ProductName =
SUBSTRING(ProductName, 1,CHARINDEX('(', ProductName) - 2)
GO

-- For each product, select the lowest non-future
-- price that has not been superseded.
SELECT ProductName, MIN(Price) as Price -- get the lowest price

FROM (

SELECT ProductName, Price -- from all non-future prices
FROM ProductList P1
WHERE P1.EffectiveDate <= CURRENT_TIMESTAMP
AND NOT EXISTS ( -- that have not been superseded
SELECT * FROM ProductList P2
WHERE P2.Distributor = P1.Distributor
AND P2.ProductName = P1.ProductName
AND P2.EffectiveDate <= CURRENT_TIMESTAMP
AND P2.EffectiveDate > P1.EffectiveDate
)
) T
GROUP BY ProductName -- for each product
go

By the way, the delimited data was no trouble. I pasted it into
Excel, did Text To Columns, named the data region, and inserted it with:

insert into [ProductList]
select Manufacturer, ProductName, Price, EffectiveDate

from OpenRowset(

'Microsoft.Jet.OLEDB.4.0',
'Excel 8.0;Database=e:\excel\ProductList.xls',
'select * from ProductList')

Be sure to close the Excel file before inserting.

-- Steve Kass
-- Drew University
-- Ref: 2498EA13-1756-4C81-9307-25AFD5BB451D

netpurpose wrote:
>Hi Jag,
>
>Thanks a lot!! It works like a charm! Your query saves me a lot of headache.
>
>I have struggled with this for quite a while now and I am glad I find help here.
>
>Again, thank you very much! I really appreciate your help in such a short time!
>
>Regards,
>Netpurpose
>
>
>"John Gilson" <ja*@acm.org> wrote in message
news:<am*********************@twister.nyc.rr.com>. ..

>>"netpurpose" <ne********@hotmail.com> wrote in message
>>news:31**************************@posting.go ogle.com...
>>
>>
>>
>>>Hi Jag,
>>>
>>>Thank you for your response. I tried the query, but it gives me a
>>>different pricing result:
>>>
>>>ProductName Price
>>>---------------------------------------- ---------------------
>>>Product One (MXT234) 28.1500
>>>Product Two (DGT6789) 44.3500
>>>Product Three (QAT556) 40.1500
>>>
>>>The correct result should be:
>>>
>>>ProductName Price
>>>---------------------------------------- ---------------------
>>>Product One 33.5000
>>>Product Two 44.7500
>>>Product Three 40.4500
>>>
>>>The reason is because for Product One, Manufacturer "BBB" has a price
>>>of 28.15 on 2003-07-30, this price is no longer valid because "BBB"
>>>has more recent price of 33.5 starting on 2003-08-27. Same case with
>>>Product Two and Three (manufacturer "JJJ" overrides the 40.15 on
>>>2003-08-01 with 40.45 on 2003-08-04).
>>>
>>>I have to take the most recent prices from each manufacturer for a
>>>particular product (price at the latest date as of today), and then
>>>take the minimum price from the result.
>>>
>>>Again, thank you for your help. Sorry I might not explain it well in
>>>the beginning. Any further help is appreciated. Thank you very much
>>>in advance!
>>>
>>>Regards,
>>>Netpurpose
>>
>>I was a little too quick on the draw and misread your requirements.
>>
>>SELECT ProductName, MIN(Price)
>
>>FROM (SELECT P1.Distributor,
>
>
>> SUBSTRING(P1.ProductName, 1,
>> CHARINDEX('(', P1.ProductName) - 2) AS
>> ProductName,
>> P1.EffectiveDate AS LatestDate,
>> P1.price
>> FROM ProductList AS P1
>> LEFT OUTER JOIN
>> ProductList AS P2
>> ON P1.Distributor = P2.Distributor AND
>> P1.ProductName = P2.ProductName AND
>> P1.EffectiveDate <= CURRENT_TIMESTAMP AND
>> P2.EffectiveDate <= CURRENT_TIMESTAMP AND
>> P2.EffectiveDate > P1.EffectiveDate
>> WHERE P2.EffectiveDate IS NULL) AS LatestPrices
>>GROUP BY ProductName
>>
>>Regards,
>>jag
>>
>>
>>
>>
>>>"John Gilson" <ja*@acm.org> wrote in message
news:<_u*********************@twister.nyc.rr.com>. ..
>
>>>>"netpurpose" <ne********@hotmail.com> wrote in message
>>>>news:31**************************@posting. google.com...
>>>>
>>>>
>>>>
>>>>>I need to extract data from this table to find the lowest prices of
>>>>>each product as of today. The product will be listed/grouped by the
>>>>>name only, discarding the product code - I use SUBSTRING(ProductName,
>>>>>1, CHARINDEX('(', ProductName)-2).
>>>>>
>>>>>I can get this result, but I had to use several views (totally
>>>>>inefficient). I think this can be done in one efficient/fast query,
>>>>>but I can't think of one.
>>>>>
>>>>>In the case that one query is not possible, is there other efficient
>>>>>way to get the results? There are about 300K records in the table.
>>>>>
>>>>>Any help is appreciated! Thanks a lot in advance!
>>>>>
>>>>>Thanks,
>>>>>Netpurpose
>>>>
>>>>SELECT P1.ProductName, P1.Price
>>>
>>>>FROM ProductList AS P1
>>>
>>>
>>>>WHERE EffectiveDate <= CURRENT_TIMESTAMP AND
>>>> NOT EXISTS
>>>> (SELECT *
>>>> FROM ProductList AS P2
>>>> WHERE SUBSTRING(P1.ProductName, 1,
>>>> CHARINDEX('(', P1.ProductName) - 2) =
>>>> SUBSTRING(P2.ProductName, 1,
>>>> CHARINDEX('(', P2.ProductName) - 2)
AND
>> P2.EffectiveDate <= CURRENT_TIMESTAMP AND
>>>> P2.Price < P1.Price)
>>>>
>>>>Regards,
>>>>jag
>>>>
>>>>



Jul 20 '05 #8

P: n/a
"Steve Kass" <sk***@drew.edu> wrote in message
news:dG******************@newsread2.news.atl.earth link.net...
John,

I hate to be a pest, but I believe you need the
date restriction in two places. The query here will
fail if the lowest price for a product comes from a
distributor that has already announced a price to become
effective in the future. If that is true, the future
price will come up on the right side of the join, since
there is no date restriction there. That makes the value
of P2.EffectiveDate not null and in the future, and the
P1.Price in that row, despite being the lowest for the
product, is filtered out.

Ok, I lied - I don't hate being a pest, but I do
think your query doesn't quite work.

Steve
Steve, I don't hate you for being a pest. Ok, I lied - I do hate you
for being a pest but, of course, you happen to also be correct (again!)
so, to a small extent, it assuages your pestiferousness. But seriously,
in my haste, I seemed to have dropped a condition that I had originally
specified in the outer join, that is,
P2.EffectiveDate <= CURRENT_TIMESTAMP
Putting this back in leaves us with

SELECT ProductName, MIN(Price) AS Price
FROM (SELECT P1.Distributor,
SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) AS
ProductName,
P1.EffectiveDate AS LatestDate,
P1.price
FROM ProductList AS P1
LEFT OUTER JOIN
ProductList AS P2
ON P1.Distributor = P2.Distributor AND
P1.ProductName = P2.ProductName AND
P2.EffectiveDate > P1.EffectiveDate AND
P2.EffectiveDate <= CURRENT_TIMESTAMP
WHERE P2.EffectiveDate IS NULL AND
P1.EffectiveDate <= CURRENT_TIMESTAMP)
AS LatestPrices
GROUP BY ProductName

And Steve, thanks for the sharp eye and sharper mind.

Regards,
jag
John Gilson wrote:
"Steve Kass" <sk***@drew.edu> wrote in message
news:u5*****************@newsread2.news.atl.earthl ink.net...
When I ran John's query on your sample data, It
returned the price of $25.04 for Product One, a price
that was not effective on the day I ran the query.

Make sure your sample data has some examples where
the lowest price is a future price that has been
recorded but is not yet effective.

Steve, you're absolutely right and stems from the (mis)placement
of the selection criteria for the outer join. The constraint
P1.EffectiveDate <= CURRENT_TIMESTAMP
should be applied *after* the outer join condition, that is, in the
WHERE clause. So this should do the right thing:

SELECT ProductName, MIN(Price)
FROM (SELECT P1.Distributor,
SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) AS
ProductName,
P1.EffectiveDate AS LatestDate,
P1.price
FROM ProductList AS P1
LEFT OUTER JOIN
ProductList AS P2
ON P1.Distributor = P2.Distributor AND
P1.ProductName = P2.ProductName AND
P2.EffectiveDate > P1.EffectiveDate
WHERE P2.EffectiveDate IS NULL AND
P1.EffectiveDate <= CURRENT_TIMESTAMP)
AS LatestPrices
GROUP BY ProductName

Regards,
jag

As far as efficiency goes, all I did was look at query
plans. What I found was that John's query and mine
had virtually identical plans.

What I did was this:

Removed the part of product name in parentheses. If that data
is important, it should be a separate column. I removed it,
since to make this efficient there needed (I think) to be an
index with the ProductName value you want in the output, without
the extra comment, as the first column.

Removed all cases where the same (ProductName, Distributor,
EffectiveDate) appeared in more than one row (these probably
appeared when I removed the extra part of the product name).

Declared (ProductName, Distributor, EffectiveDate) to be the
primary key. Maybe I missed something and this does not work
as a key, but it seemed like a good choice for an index to
make the query fast. If it's not a key, add price as
a fourth column.

I realized now that there was extra nesting in my query.
I don't think it should have slowed it down tenfold, but the
outer two selects can be combined (if the data has no duplicates
in my key columns).
-- Select the lowest price
SELECT ProductName, MIN(Price)

-- from the table
FROM ProductList P1

-- that is not a future price
WHERE P1.EffectiveDate <= CURRENT_TIMESTAMP

-- and that has not been superseded
AND NOT EXISTS (
-- by another price
SELECT * FROM ProductList P2
-- from the same distributor
WHERE P2.Distributor = P1.Distributor
-- for the same product
AND P2.ProductName = P1.ProductName
-- which other price has gone into effect
AND P2.EffectiveDate <= CURRENT_TIMESTAMP
-- more recently
AND P2.EffectiveDate > P1.EffectiveDate
)

-- for each product
GROUP BY ProductName

Steve
netpurpose wrote:

Hi Steve,

Thanks for your response. When I copied John's query, it works fine
and gives me the correct results. I did run both your query and his
against 330K of records, and it seems that his query runs much faster
(more than 10 times faster). I ran your query against clean products
names without the codes.

I am too novice to even know why the big difference. Both query
yields the same results. Can you tell why his statement is much more
efficient? LEFT OUTER JOIN vs EXISTS? I do want to learn from this.

Also, thanks for showing me the command to import the excel file to
db. Good to know :)

Thanks,
Netpurpose

Steve Kass <sk***@drew.edu> wrote in message


news:<xW*****************@newsread2.news.atl.earth link.net>...
>Did I miscopy John's query? It gives me the future price of $25.04
>for Product One, but is easy to fix by adding
>
> AND P1.EffectiveDate <= CURRENT_TIMESTAMP
>
>to the where clause of the derived table LatestPrices
>
>John's initial idea of NOT EXISTS still works, too, in part. (Note
>that I blew off the ProductName parsing by taking a hatchet to that
>column with an update...
>
>
>-- Be lazy
>UPDATE ProductList SET
> ProductName =
> SUBSTRING(ProductName, 1,CHARINDEX('(', ProductName) - 2)
>GO
>
>-- For each product, select the lowest non-future
>-- price that has not been superseded.
>SELECT ProductName, MIN(Price) as Price -- get the lowest price

>FROM (

> SELECT ProductName, Price -- from all non-future prices
> FROM ProductList P1
> WHERE P1.EffectiveDate <= CURRENT_TIMESTAMP
> AND NOT EXISTS ( -- that have not been superseded
> SELECT * FROM ProductList P2
> WHERE P2.Distributor = P1.Distributor
> AND P2.ProductName = P1.ProductName
> AND P2.EffectiveDate <= CURRENT_TIMESTAMP
> AND P2.EffectiveDate > P1.EffectiveDate
> )
>) T
>GROUP BY ProductName -- for each product
>go
>
>By the way, the delimited data was no trouble. I pasted it into
>Excel, did Text To Columns, named the data region, and inserted it with:
>
>insert into [ProductList]
>select Manufacturer, ProductName, Price, EffectiveDate

>from OpenRowset(

> 'Microsoft.Jet.OLEDB.4.0',
> 'Excel 8.0;Database=e:\excel\ProductList.xls',
> 'select * from ProductList')
>
>Be sure to close the Excel file before inserting.
>
>-- Steve Kass
>-- Drew University
>-- Ref: 2498EA13-1756-4C81-9307-25AFD5BB451D
>
>
>
>netpurpose wrote:
>
>
>>Hi Jag,
>>
>>Thanks a lot!! It works like a charm! Your query saves me a lot of headache.
>>
>>I have struggled with this for quite a while now and I am glad I find help here.
>>
>>Again, thank you very much! I really appreciate your help in such a short time!
>>
>>Regards,
>>Netpurpose
>>
>>
>>"John Gilson" <ja*@acm.org> wrote in message


news:<am*********************@twister.nyc.rr.com>. ..
>>
>>>"netpurpose" <ne********@hotmail.com> wrote in message
>>>news:31**************************@posting.go ogle.com...
>>>
>>>
>>>
>>>>Hi Jag,
>>>>
>>>>Thank you for your response. I tried the query, but it gives me a
>>>>different pricing result:
>>>>
>>>>ProductName Price
>>>>---------------------------------------- ---------------------
>>>>Product One (MXT234) 28.1500
>>>>Product Two (DGT6789) 44.3500
>>>>Product Three (QAT556) 40.1500
>>>>
>>>>The correct result should be:
>>>>
>>>>ProductName Price
>>>>---------------------------------------- ---------------------
>>>>Product One 33.5000
>>>>Product Two 44.7500
>>>>Product Three 40.4500
>>>>
>>>>The reason is because for Product One, Manufacturer "BBB" has a price
>>>>of 28.15 on 2003-07-30, this price is no longer valid because "BBB"
>>>>has more recent price of 33.5 starting on 2003-08-27. Same case with
>>>>Product Two and Three (manufacturer "JJJ" overrides the 40.15 on
>>>>2003-08-01 with 40.45 on 2003-08-04).
>>>>
>>>>I have to take the most recent prices from each manufacturer for a
>>>>particular product (price at the latest date as of today), and then
>>>>take the minimum price from the result.
>>>>
>>>>Again, thank you for your help. Sorry I might not explain it well in
>>>>the beginning. Any further help is appreciated. Thank you very much
>>>>in advance!
>>>>
>>>>Regards,
>>>>Netpurpose
>>>
>>>I was a little too quick on the draw and misread your requirements.
>>>
>>>SELECT ProductName, MIN(Price)
>>
>>>FROM (SELECT P1.Distributor,
>>
>>
>>> SUBSTRING(P1.ProductName, 1,
>>> CHARINDEX('(', P1.ProductName) - 2) AS
>>> ProductName,
>>> P1.EffectiveDate AS LatestDate,
>>> P1.price
>>> FROM ProductList AS P1
>>> LEFT OUTER JOIN
>>> ProductList AS P2
>>> ON P1.Distributor = P2.Distributor AND
>>> P1.ProductName = P2.ProductName AND
>>> P1.EffectiveDate <= CURRENT_TIMESTAMP AND
>>> P2.EffectiveDate <= CURRENT_TIMESTAMP AND
>>> P2.EffectiveDate > P1.EffectiveDate
>>> WHERE P2.EffectiveDate IS NULL) AS LatestPrices
>>>GROUP BY ProductName
>>>
>>>Regards,
>>>jag
>>>
>>>
>>>
>>>
>>>>"John Gilson" <ja*@acm.org> wrote in message


news:<_u*********************@twister.nyc.rr.com>. ..
>>>>
>>>>>"netpurpose" <ne********@hotmail.com> wrote in message
>>>>>news:31**************************@posting. google.com...
>>>>>
>>>>>
>>>>>
>>>>>>I need to extract data from this table to find the lowest prices of
>>>>>>each product as of today. The product will be listed/grouped by the
>>>>>>name only, discarding the product code - I use SUBSTRING(ProductName,
>>>>>>1, CHARINDEX('(', ProductName)-2).
>>>>>>
>>>>>>I can get this result, but I had to use several views (totally
>>>>>>inefficient). I think this can be done in one efficient/fast query,
>>>>>>but I can't think of one.
>>>>>>
>>>>>>In the case that one query is not possible, is there other efficient
>>>>>>way to get the results? There are about 300K records in the table.
>>>>>>
>>>>>>Any help is appreciated! Thanks a lot in advance!
>>>>>>
>>>>>>Thanks,
>>>>>>Netpurpose
>>>>>
>>>>>SELECT P1.ProductName, P1.Price
>>>>
>>>>>FROM ProductList AS P1
>>>>
>>>>
>>>>>WHERE EffectiveDate <= CURRENT_TIMESTAMP AND
>>>>> NOT EXISTS
>>>>> (SELECT *
>>>>> FROM ProductList AS P2
>>>>> WHERE SUBSTRING(P1.ProductName, 1,
>>>>> CHARINDEX('(', P1.ProductName) - 2) =
>>>>> SUBSTRING(P2.ProductName, 1,
>>>>> CHARINDEX('(', P2.ProductName) - 2)


AND
>>>>> P2.EffectiveDate <= CURRENT_TIMESTAMP AND
>>>>> P2.Price < P1.Price)
>>>>>
>>>>>Regards,
>>>>>jag
>>>>>
>>>>>


Jul 20 '05 #9

P: n/a


John Gilson wrote:
"Steve Kass" <sk***@drew.edu> wrote in message
news:dG******************@newsread2.news.atl.earth link.net...
John,

I hate to be a pest, but I believe you need the
date restriction in two places. The query here will
fail if the lowest price for a product comes from a
distributor that has already announced a price to become
effective in the future. If that is true, the future
price will come up on the right side of the join, since
there is no date restriction there. That makes the value
of P2.EffectiveDate not null and in the future, and the
P1.Price in that row, despite being the lowest for the
product, is filtered out.

Ok, I lied - I don't hate being a pest, but I do
think your query doesn't quite work.

Steve

Steve, I don't hate you for being a pest. Ok, I lied - I do hate you
for being a pest but, of course, you happen to also be correct (again!)
so, to a small extent, it assuages your pestiferousness. But seriously,
in my haste, I seemed to have dropped a condition that I had originally
specified in the outer join, that is,
P2.EffectiveDate <= CURRENT_TIMESTAMP
Putting this back in leaves us with

SELECT ProductName, MIN(Price) AS Price
FROM (SELECT P1.Distributor,
SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) AS
ProductName,
P1.EffectiveDate AS LatestDate,
P1.price
FROM ProductList AS P1
LEFT OUTER JOIN
ProductList AS P2
ON P1.Distributor = P2.Distributor AND
P1.ProductName = P2.ProductName AND
P2.EffectiveDate > P1.EffectiveDate AND
P2.EffectiveDate <= CURRENT_TIMESTAMP
WHERE P2.EffectiveDate IS NULL AND
P1.EffectiveDate <= CURRENT_TIMESTAMP)
AS LatestPrices
GROUP BY ProductName

And Steve, thanks for the sharp eye and sharper mind.


Don't mention it. Now if I could only do something about the matching
tongue.

Steve

Regards,
jag

John Gilson wrote:
"Steve Kass" <sk***@drew.edu> wrote in message
news:u5*****************@newsread2.news.atl.ear thlink.net...
When I ran John's query on your sample data, It
returned the price of $25.04 for Product One, a price
that was not effective on the day I ran the query.

Make sure your sample data has some examples where
the lowest price is a future price that has been
recorded but is not yet effective.
Steve, you're absolutely right and stems from the (mis)placement
of the selection criteria for the outer join. The constraint
P1.EffectiveDate <= CURRENT_TIMESTAMP
should be applied *after* the outer join condition, that is, in the
WHERE clause. So this should do the right thing:

SELECT ProductName, MIN(Price)
FROM (SELECT P1.Distributor,
SUBSTRING(P1.ProductName, 1,
CHARINDEX('(', P1.ProductName) - 2) AS
ProductName,
P1.EffectiveDate AS LatestDate,
P1.price
FROM ProductList AS P1
LEFT OUTER JOIN
ProductList AS P2
ON P1.Distributor = P2.Distributor AND
P1.ProductName = P2.ProductName AND
P2.EffectiveDate > P1.EffectiveDate
WHERE P2.EffectiveDate IS NULL AND
P1.EffectiveDate <= CURRENT_TIMESTAMP)
AS LatestPrices
GROUP BY ProductName

Regards,
jag

As far as efficiency goes, all I did was look at query
plans. What I found was that John's query and mine
had virtually identical plans.

What I did was this:

Removed the part of product name in parentheses. If that data
is important, it should be a separate column. I removed it,
since to make this efficient there needed (I think) to be an
index with the ProductName value you want in the output, without
the extra comment, as the first column.

Removed all cases where the same (ProductName, Distributor,
EffectiveDate) appeared in more than one row (these probably
appeared when I removed the extra part of the product name).

Declared (ProductName, Distributor, EffectiveDate) to be the
primary key. Maybe I missed something and this does not work
as a key, but it seemed like a good choice for an index to
make the query fast. If it's not a key, add price as
a fourth column.

I realized now that there was extra nesting in my query.
I don't think it should have slowed it down tenfold, but the
outer two selects can be combined (if the data has no duplicates
in my key columns).
-- Select the lowest price
SELECT ProductName, MIN(Price)

-- from the table

FROM ProductList P1

-- that is not a future price
WHERE P1.EffectiveDate <= CURRENT_TIMESTAMP

-- and that has not been superseded
AND NOT EXISTS (
-- by another price
SELECT * FROM ProductList P2
-- from the same distributor
WHERE P2.Distributor = P1.Distributor
-- for the same product
AND P2.ProductName = P1.ProductName
-- which other price has gone into effect
AND P2.EffectiveDate <= CURRENT_TIMESTAMP
-- more recently
AND P2.EffectiveDate > P1.EffectiveDate
)

-- for each product
GROUP BY ProductName

Steve
netpurpose wrote:
>Hi Steve,
>
>Thanks for your response. When I copied John's query, it works fine
>and gives me the correct results. I did run both your query and his
>against 330K of records, and it seems that his query runs much faster
>(more than 10 times faster). I ran your query against clean products
>names without the codes.
>
>I am too novice to even know why the big difference. Both query
>yields the same results. Can you tell why his statement is much more
>efficient? LEFT OUTER JOIN vs EXISTS? I do want to learn from this.
>
>Also, thanks for showing me the command to import the excel file to
>db. Good to know :)
>
>Thanks,
>Netpurpose
>
>Steve Kass <sk***@drew.edu> wrote in message

news:<xW*****************@newsread2.news.atl.ea rthlink.net>...
>>Did I miscopy John's query? It gives me the future price of $25.04
>>for Product One, but is easy to fix by adding
>>
>> AND P1.EffectiveDate <= CURRENT_TIMESTAMP
>>
>>to the where clause of the derived table LatestPrices
>>
>>John's initial idea of NOT EXISTS still works, too, in part. (Note
>>that I blew off the ProductName parsing by taking a hatchet to that
>>column with an update...
>>
>>
>>-- Be lazy
>>UPDATE ProductList SET
>> ProductName =
>> SUBSTRING(ProductName, 1,CHARINDEX('(', ProductName) - 2)
>>GO
>>
>>-- For each product, select the lowest non-future
>>-- price that has not been superseded.
>>SELECT ProductName, MIN(Price) as Price -- get the lowest price
>
>>FROM (
>
>
>> SELECT ProductName, Price -- from all non-future prices
>> FROM ProductList P1
>> WHERE P1.EffectiveDate <= CURRENT_TIMESTAMP
>> AND NOT EXISTS ( -- that have not been superseded
>> SELECT * FROM ProductList P2
>> WHERE P2.Distributor = P1.Distributor
>> AND P2.ProductName = P1.ProductName
>> AND P2.EffectiveDate <= CURRENT_TIMESTAMP
>> AND P2.EffectiveDate > P1.EffectiveDate
>> )
>>) T
>>GROUP BY ProductName -- for each product
>>go
>>
>>By the way, the delimited data was no trouble. I pasted it into
>>Excel, did Text To Columns, named the data region, and inserted it with:
>>
>>insert into [ProductList]
>>select Manufacturer, ProductName, Price, EffectiveDate
>
>>from OpenRowset(
>
>
>> 'Microsoft.Jet.OLEDB.4.0',
>> 'Excel 8.0;Database=e:\excel\ProductList.xls',
>> 'select * from ProductList')
>>
>>Be sure to close the Excel file before inserting.
>>
>>-- Steve Kass
>>-- Drew University
>>-- Ref: 2498EA13-1756-4C81-9307-25AFD5BB451D
>>
>>
>>
>>netpurpose wrote:
>>
>>
>>
>>>Hi Jag,
>>>
>>>Thanks a lot!! It works like a charm! Your query saves me a lot of headache.
>>>
>>>I have struggled with this for quite a while now and I am glad I find help here.
>>>
>>>Again, thank you very much! I really appreciate your help in such a short time!
>>>
>>>Regards,
>>>Netpurpose
>>>
>>>
>>>"John Gilson" <ja*@acm.org> wrote in message

news:<am*********************@twister.nyc.rr.co m>...
>>>>"netpurpose" <ne********@hotmail.com> wrote in message
>>>>news:31**************************@posting. google.com...
>>>>
>>>>
>>>>
>>>>
>>>>>Hi Jag,
>>>>>
>>>>>Thank you for your response. I tried the query, but it gives me a
>>>>>different pricing result:
>>>>>
>>>>>ProductName Price
>>>>>---------------------------------------- ---------------------
>>>>>Product One (MXT234) 28.1500
>>>>>Product Two (DGT6789) 44.3500
>>>>>Product Three (QAT556) 40.1500
>>>>>
>>>>>The correct result should be:
>>>>>
>>>>>ProductName Price
>>>>>---------------------------------------- ---------------------
>>>>>Product One 33.5000
>>>>>Product Two 44.7500
>>>>>Product Three 40.4500
>>>>>
>>>>>The reason is because for Product One, Manufacturer "BBB" has a price
>>>>>of 28.15 on 2003-07-30, this price is no longer valid because "BBB"
>>>>>has more recent price of 33.5 starting on 2003-08-27. Same case with
>>>>>Product Two and Three (manufacturer "JJJ" overrides the 40.15 on
>>>>>2003-08-01 with 40.45 on 2003-08-04).
>>>>>
>>>>>I have to take the most recent prices from each manufacturer for a
>>>>>particular product (price at the latest date as of today), and then
>>>>>take the minimum price from the result.
>>>>>
>>>>>Again, thank you for your help. Sorry I might not explain it well in
>>>>>the beginning. Any further help is appreciated. Thank you very much
>>>>>in advance!
>>>>>
>>>>>Regards,
>>>>>Netpurpose
>>>>
>>>>I was a little too quick on the draw and misread your requirements.
>>>>
>>>>SELECT ProductName, MIN(Price)
>>>
>>>>FROM (SELECT P1.Distributor,
>>>
>>>
>>>
>>>> SUBSTRING(P1.ProductName, 1,
>>>> CHARINDEX('(', P1.ProductName) - 2) AS
>>>> ProductName,
>>>> P1.EffectiveDate AS LatestDate,
>>>> P1.price
>>>> FROM ProductList AS P1
>>>> LEFT OUTER JOIN
>>>> ProductList AS P2
>>>> ON P1.Distributor = P2.Distributor AND
>>>> P1.ProductName = P2.ProductName AND
>>>> P1.EffectiveDate <= CURRENT_TIMESTAMP AND
>>>> P2.EffectiveDate <= CURRENT_TIMESTAMP AND
>>>> P2.EffectiveDate > P1.EffectiveDate
>>>> WHERE P2.EffectiveDate IS NULL) AS LatestPrices
>>>>GROUP BY ProductName
>>>>
>>>>Regards,
>>>>jag
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>>"John Gilson" <ja*@acm.org> wrote in message

news:<_u*********************@twister.nyc.rr.co m>...
>>>>>>"netpurpose" <ne********@hotmail.com> wrote in message
>>>>>>news:31**************************@postin g.google.com...
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>>I need to extract data from this table to find the lowest prices of
>>>>>>>each product as of today. The product will be listed/grouped by the
>>>>>>>name only, discarding the product code - I use SUBSTRING(ProductName,
>>>>>>>1, CHARINDEX('(', ProductName)-2).
>>>>>>>
>>>>>>>I can get this result, but I had to use several views (totally
>>>>>>>inefficient). I think this can be done in one efficient/fast query,
>>>>>>>but I can't think of one.
>>>>>>>
>>>>>>>In the case that one query is not possible, is there other efficient
>>>>>>>way to get the results? There are about 300K records in the table.
>>>>>>>
>>>>>>>Any help is appreciated! Thanks a lot in advance!
>>>>>>>
>>>>>>>Thanks,
>>>>>>>Netpurpose
>>>>>>
>>>>>>SELECT P1.ProductName, P1.Price
>>>>>
>>>>>>FROM ProductList AS P1
>>>>>
>>>>>
>>>>>
>>>>>>WHERE EffectiveDate <= CURRENT_TIMESTAMP AND
>>>>>> NOT EXISTS
>>>>>> (SELECT *
>>>>>> FROM ProductList AS P2
>>>>>> WHERE SUBSTRING(P1.ProductName, 1,
>>>>>> CHARINDEX('(', P1.ProductName) - 2) =
>>>>>> SUBSTRING(P2.ProductName, 1,
>>>>>> CHARINDEX('(', P2.ProductName) - 2)

AND
>>>>>> P2.EffectiveDate <= CURRENT_TIMESTAMP AND
>>>>>> P2.Price < P1.Price)
>>>>>>
>>>>>>Regards,
>>>>>>jag
>>>>>>
>>>>>>



Jul 20 '05 #10

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