I am new to bitwise thing in MSSQL.
Let's suppose there's a table of favorite foods
insert int fav_foods(food_name,bitwiseVal)
values('Pasta',1)
insert int fav_foods(food_name,bitwiseVal)
values('Chicken',2)
insert int fav_foods(food_name,bitwiseVal)
values('Beef',4)
insert int fav_foods(food_name,bitwiseVal)
values('Fish',8)
insert int fav_foods(food_name,bitwiseVal)
values('Pork',16)
How do I write query to find people who selected more than one item and
selected items from "Pasta, Chicken, Beef, Pork"(but not fish)?
I hope my question is not confusing..... 6 5894
Bostonasian wrote: I am new to bitwise thing in MSSQL.
Let's suppose there's a table of favorite foods
insert int fav_foods(food_name,bitwiseVal) values('Pasta',1)
insert int fav_foods(food_name,bitwiseVal) values('Chicken',2)
insert int fav_foods(food_name,bitwiseVal) values('Beef',4)
insert int fav_foods(food_name,bitwiseVal) values('Fish',8)
insert int fav_foods(food_name,bitwiseVal) values('Pork',16)
How do I write query to find people who selected more than one item and selected items from "Pasta, Chicken, Beef, Pork"(but not fish)? I hope my question is not confusing.....
Your question isn't confusing but your design decision is. Why use
bitwise on something like this? If you were to use proper table design
this query would be trivial (and fast).
Zach
I tried to simply the example as much as possible, that's probably why
it didn't look that neccesary to build table like this.
I actually have survey data. Survey answer includes text, single select
multiple choice and multi-select multiple choice.
In answered data table, I currently have schema like following :
customer | question_id | answer
-----------------------------------------------
John | 1 | Pasta
John | 1 | Beef
John | 1 | Chicken
John | 1 | Pork
And I've got 2.4 million customers to manage, so I thought it'd save
some rows by using bitwise to reduce row numbers to one.
Bostonasian wrote: I tried to simply the example as much as possible, that's probably why it didn't look that neccesary to build table like this.
I actually have survey data. Survey answer includes text, single select multiple choice and multi-select multiple choice.
In answered data table, I currently have schema like following :
customer | question_id | answer ----------------------------------------------- John | 1 | Pasta John | 1 | Beef John | 1 | Chicken John | 1 | Pork
And I've got 2.4 million customers to manage, so I thought it'd save some rows by using bitwise to reduce row numbers to one.
What you save in rows (i.e. disk space, which is cheap), you'll likely
lose in readability, mainainability, performance and standardization.
Search out one of Joe Celko's rants about thinking like a procedural
programmer and not a SQL/set based programmer because I think that's the
problem here.
Zach
> And I've got 2.4 million customers to manage, so I thought it'd save some rows by using bitwise to reduce row numbers to one.
I'll bet that disk space is much cheaper than the cost of the time you'll
spend fixing up a kludge like that :-)
Try this:
CREATE TABLE Foods (customer_id INTEGER NOT NULL REFERENCES Customers
(customer_id), food INTEGER NOT NULL REFERENCES Foods (food), PRIMARY KEY
(customer_id, food))
SELECT customer_id
FROM Foods
WHERE food IN (1,2,3,4,5) /* Pasta,Chicken,Beef,Pork,Fish */
GROUP BY customer_id
HAVING COUNT(CASE WHEN food IN (1,2,3,4) THEN 1 END) = COUNT(*)
/* Everything except fish */
--
David Portas
SQL Server MVP
--
Bostonasian (ax****@gmail.com) writes: I am new to bitwise thing in MSSQL.
Let's suppose there's a table of favorite foods
insert int fav_foods(food_name,bitwiseVal) values('Pasta',1)
insert int fav_foods(food_name,bitwiseVal) values('Chicken',2)
insert int fav_foods(food_name,bitwiseVal) values('Beef',4)
insert int fav_foods(food_name,bitwiseVal) values('Fish',8)
insert int fav_foods(food_name,bitwiseVal) values('Pork',16)
How do I write query to find people who selected more than one item and selected items from "Pasta, Chicken, Beef, Pork"(but not fish)? I hope my question is not confusing.....
SELECT *
FROM tbl
WHERE fav_food & (SELECT SUM(bitwiseVal)
FROM fav_foods
WHERE food_name IN ('Pasta', 'Chicken', 'Beef', 'Pork'))
But as pointed out by others, this is a poor design. You may
save disk space, but if you need to find all that selected Chicken,
you will find that you cannot have an index on bit in an integer
column, so you get awful performance.
Look at David's query, and use that instead of the above.
--
Erland Sommarskog, SQL Server MVP, es****@sommarskog.se
Books Online for SQL Server SP3 at http://www.microsoft.com/sql/techinf...2000/books.asp
Bostonasian wrote: I tried to simply the example as much as possible, that's probably why it didn't look that neccesary to build table like this.
I actually have survey data. Survey answer includes text, single select multiple choice and multi-select multiple choice.
In answered data table, I currently have schema like following :
customer | question_id | answer ----------------------------------------------- John | 1 | Pasta John | 1 | Beef John | 1 | Chicken John | 1 | Pork
And I've got 2.4 million customers to manage, so I thought it'd save some rows by using bitwise to reduce row numbers to one.
Hi Bostonasian,
There is no need to denormalize or use bitwise operations for this. IMO,
bitwise operations are not suitable for this problem.
The database does not have to grow very fast. If you normalize all the
way through, you would get a Customers (reference) table, a Questions
(reference) table and a Answers (reference) table. All these reference
tables can have short keys, which you use in your CustomerAnswers (data)
table. If you have fewer than 64000 customers, fewer than 256 questions
and fewer than 256 (fixed) answers per question, then each row in
CustomerAnswers would be just 2+1+1 = 4 bytes (excluding the free format
text answers).
Your schema could look something like this:
CREATE TABLE Customers(CustomerID smallint PRIMARY KEY, Name
nvarchar(100))
CREATE TABLE Questions(QuestionID tinyint PRIMARY KEY, Question
nvarchar(3000))
CREATE TABLE Answers (QuestionID tinyint, AnswerID tinyint, Answer
nvarchar(200),PRIMARY KEY (QuestionID,AnswerID))
CREATE TABLE CustomerAnswers
(CustomerID smallint REFERENCES Customers
,QuestionID tinyint REFERENCES Questions
,AnswerID tinyint
,TextAnswer nvarchar(2000)
,PRIMARY KEY (CustomerID,QuestionID,AnswerID)
,FOREIGN KEY (QuestionID,AnswerID) REFERENCES Answers
)
Hope this helps,
Gert-Jan This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
by: jas_lx |
last post by:
The basic understanding of what bitwise operators (& ^ | >> << ) comes
fairly simple, as long as one has a fundamental understanding of bits,
bytes and binary.
Having done some Win32...
|
by: Steve Summit |
last post by:
-----BEGIN PGP SIGNED MESSAGE-----
It's often explained that the reason for some of the imprecision
in C's definition is so that C can be implemented on different
kinds of machines -- say, those...
|
by: Paul E Collins |
last post by:
Suppose I have a few Keys objects:
Keys k1 = Keys.V; // V
Keys k2 = Keys.Control | Keys.V; // Ctrl+V
Keys k3 = Keys.Shift | Keys.J; // Shift+J
I need to determine which of these include the...
|
by: Christopher Weaver |
last post by:
I know that the bitwise AND of 8 and 4 will return 0 or false and the
bitwise AND of 8 and 9 will return 1 or true but I don't know how to write
the synax for it in C#. I have a value that ranges...
|
by: noridotjabi |
last post by:
I'm learning to program in C and any tutorial or book that I read likes
to briefly touch on birdies operators and then move on without giving
any sort of example application of them. Call me what...
| |
by: Mark Rae |
last post by:
Hi,
This isn't *specifically* an ASP.NET question, so I've also posted it in the
ADO.NET group - however, it's not too far off-topic...
Imagine a SQL Server 2005 database with a table with an...
|
by: Jay Ruyle |
last post by:
I'm trying to figure out a way to list several items in a listbox and let
the user select any number of items in the listbox. I have tried to code in
the items as bitwise items but all it stores...
|
by: Gigs_ |
last post by:
Can someone explain me bitwise expression?
few examples for every expression will be nice
x << y Left shift
x >y Right shift
x & y Bitwise AND
x | y Bitwise OR
x ^ y Bitwise XOR (exclusive...
|
by: Carramba |
last post by:
Hi!
I now that I can't do straight forward any bitwise operation on float
(double etc..). But I wondering what is the easiest/best way to do this?
I was thinking if I have float x=1.1111 so I can...
|
by: Carl Banks |
last post by:
Anyone with me here? (I know the deadline for P3 PEPs has passed; this
is just talk.)
Not many people are bit-fiddling these days. One of the main uses of bit
fields is flags, but that's not...
|
by: Hystou |
last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can...
| |
by: jinu1996 |
last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven...
|
by: Hystou |
last post by:
Overview:
Windows 11 and 10 have less user interface control over operating system update behaviour than previous versions of Windows. In Windows 11 and 10, there is no way to turn off the Windows...
|
by: tracyyun |
last post by:
Dear forum friends,
With the development of smart home technology, a variety of wireless communication protocols have appeared on the market, such as Zigbee, Z-Wave, Wi-Fi, Bluetooth, etc. Each...
|
by: agi2029 |
last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing,...
|
by: isladogs |
last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM).
In this session, we are pleased to welcome a new...
|
by: adsilva |
last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
| |
by: muto222 |
last post by:
How can i add a mobile payment intergratation into php mysql website.
|
by: bsmnconsultancy |
last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence...
| |