phantom records

[TB]

Hi all:

I realize that this is strictly speaking not an ASP.NET question, but
since most of you people out there SQL gurus as well, I hope you will
bear with me on this occasion:

I would like to know how to create a "phantom" record when running a
SELECT query.

For example:

Running "Select ID, Firstname, Lastname from Customers order by
Lastname" would produce a list all the records in the Customers table
such as:

1 John Brown
2 Anne Johnsen
3 Tom Smith
But I would like the first the result of such a query to contain a
"virtual record", i.e information that I have manually inserted into
the query and does not correspond to any record.

So, by way of an example how do I ensure a return like this:

0 PETER JENSEN
1 John Brown
2 Anne Johnsen
3 Tom Smith

when there is no record containing the information "0 Peter Jensen"?

Thanks.

TB

[sloan]

I answered it in

microsoft . public . sqlserver . programming

newsgroup.

Search by subject for "
Re: phantom records"

"TB" <tr********@gma il.com> wrote in message
news:11******** **************@ z34g2000cwc.goo glegroups.com.. .

Hi all:

I realize that this is strictly speaking not an ASP.NET question, but
since most of you people out there SQL gurus as well, I hope you will
bear with me on this occasion:

I would like to know how to create a "phantom" record when running a
SELECT query.

For example:

Running "Select ID, Firstname, Lastname from Customers order by
Lastname" would produce a list all the records in the Customers table
such as:

1 John Brown
2 Anne Johnsen
3 Tom Smith
But I would like the first the result of such a query to contain a
"virtual record", i.e information that I have manually inserted into
the query and does not correspond to any record.

So, by way of an example how do I ensure a return like this:

0 PETER JENSEN
1 John Brown
2 Anne Johnsen
3 Tom Smith

when there is no record containing the information "0 Peter Jensen"?

Thanks.

TB

[sloan]

http://groups.google.com/group/micro...7ddf6f31318af4

[Flinky Wisty Pomm]

SELECT 0 as ID,
'Peter' AS FirstName,
'Jensen' AS Surname
UNION ALL
SELECT Id,
FirstName,
Surname
FROM...

But that will insert the record and then sort. What are you doing with
the result of the query?

I suppose you could do

SELECT 0 AS ID, 'Peter' AS FirstName, 'Jensen' AS Surname, 0 AS DUMMY
UNION ALL
SELECT ID, FirstName, Surname, 1
FROM ...
ORDER BY Dummy, Surname

But that's getting uglier and uglier, why on earth would you want to do
this?

[TB]

Thanks a lot for your reply. Your last proposal works.

Now why would I want to do this? Well You see, I have this drop-down
list which is populated from a datebase. However, in addition to the
list items suppled by a table, I need some kind of default "all of the
above" (or below in case of af DDL) choice.

I have discovered that neither of the below statements:
ddlChoices.item s.add(new listitem("Defau lt",0)) 'This one adds at the
end of the list

OR

ddlchoice.items .insert(0,New listitem("Defau lt",9)) 'This one adds at
the beginning of the list

seem to be compatible with databinding from a data source, such as

ddlchoice.DataS ource = mydatareader
ddlchoice.DataV alueField = "ID"
ddlchoice.DataT extField = "Lastname"
ddlchoice.DataB ind()

If I databind after adding either of the two statements above, then
only the results from the database appear. If I add either of the two
statements after databinding then ddl will only contain one list item,
namely the manual insert.

So I came up with the idea of this phantom record.

What do you think?

TB

[TB]

One more thing:

I discovered that the columns get truncated according the length of the
dummy column. For example, the firstname column width is 5, because the
dummy record contains the 5 letter word Peter. Why is that?

Another thing is that the statement after the UNION ALL should contain
a CONCAT function.

However, if I do this:

SELECT 0 AS IDuser, '(All employees)' AS Lastname, 0 AS dummy
UNION ALL
SELECT Iduser, concat( FirstName, ' ', Lastname) AS name, 1
FROM tblUsers
ORDER BY dummy, lastname

then the secondary sort (after dummy) is done on the result of the
CONCAT operation. In other words, the (undesired) result will be

0 (All Employees) 0
2 Anne Johnsen 1
1 John Brown 1
3 Tom Smith 1
If I shorten to
SELECT 0 AS IDuser, '(All)' AS Lastname, 0 AS dummy
UNION ALL
SELECT Iduser, concat( FirstName, ' ', Lastname) AS name, 1
FROM tblUsers
ORDER BY dummy, lastname

then the result is

0 (All) 0
2 Anne 1
1 John 1
3 Tom 1

Cheers

TB

[Flinky Wisty Pomm]

Your DDL only contains one item if you insert after databinding? That's
.... odd; I've got manifold examples right here in front of me where I
do something like

locations.DataS ource = Data.GetCarLoca tions(CurrentDe alership);
locations.DataT extField = "LocationId ";
locations.DataV alueField = "LocationNa me";
locations.DataB ind();

ListItem item = new ListItem("Selec t a location", "");
locations.Items .Insert(0, item);

Without a problem.

What is mydatareader exactly?

[Flinky Wisty Pomm]

Oh, and the column length - This is off-topic, so I'll be brief. SQL
Server is guessing the data type of your columns from the first set in
the union operation. 'Peter' fits nicely as a VARCHAR(5) and the second
set is cast to that type. If you wanted to keep the columns separate
without truncating data, try CAST('PETER' as VARCHAR(xxx)) AS FirstName
where xxx is (1 + FirstName.Lengt h + Surname.Length)

[TB]

I discovered the reason, and I am the one to blame: My dataloading
routine in the page_load sub was not surrounded by "If Not
Page.IsPostBack Then [...] End if" condition. So, the whole shop was of
course reset every time I hit something.

Mydatareader is the data I pick from a MySQL database:

Imports MySql.Data.MySq lClient
Public Class searchpanel
[.....]

Dim myConnection As MySqlConnection
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
System.EventArg s) Handles MyBase.Load
myConnection = New MySqlConnection (connstring)
If Not Page.IsPostBack Then
[...]
inisearch()
End If
End sub
sub inisearch()
Dim objCommand As MySqlCommand
Dim mydatareader As MySqlDataReader
strSQL = "Select ID, Concat(firstnam e,' ',lastname) as name from
tblUsers order by lastname"
objCommand = New MySqlCommand(st rSQL, myConnection)
myConnection.Op en()
mydatareader =
objCommand.Exec uteReader(Comma ndBehavior.Clos eConnection)
ddlIDuser.DataS ource = mydatareader
ddlIDuser.DataV alueField = "ID"
ddlIDuser.DataT extField = "name"
ddlIDuser.DataB ind()
mydatareader.Cl ose()
end sub
As you can see, I use CONCAT to join firstname and lastname into one
column, but if I do that with the UNION ALLl statement, then the
sorting will be from left to right in the combined field, and not on
the lastname.

Anyway, I will now try to go back to my original idea of inserting a
listitem after databinding as the error in the page_load sub has been
corrected.

[TB]

Interesting. Thanks for the info.
I have replied separately to your other posting.

TB