If Statement Query

rsm42 · February 16th, 2007, 01:57 PM

Hi,

I am working on an if statement that I want to check if a unique value , which is stored in the session object, is already inserted into a database's table. Thus the coding would be something like :

* Connect to database and table

* If unique value = session "(Value") update the database

Else insert this value into the table

Now within asp.net I assume you would use the select command with an sql statement to do this, but how exactly should I do this ?

e.g Dim queryString As String = "SELECT [tblxxx].[value] FROM [tblxxx]"

If [tblxxx].[value] = Session("value") ......

However this results in an error stating "Name [tblxxx] is not declared"....

Any examples would help ? I'm using asp.net 1.1 with vb.net and connecting to an access database.

Thanks,

dparsons · February 16th, 2007, 02:04 PM

This is all relative to what you are placing your data in (Datareader, datatable, dataset), but its the same concept for all of them.

I will assume that you are placing the resultset in a datatable

If Convert.ToString(dt.rows(0).item("columnName")) = Convert.ToString(Session("value")) then
'do something
End if

Where dt is your DataTable object.

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rsm42 · February 17th, 2007, 06:52 AM

Thanks,

I've developed some code as below but suspect the first part of the SQL statement i.e. the bit that checks if there is a CARTID already inserted, is not quite right. However no errors are displayed. Basically I want to say :

Look within the table and if CartID equals zero, i.e. it does not exist in the table, then insert values into the table.

Here's the code - any ideas :

Code:

 Dim strSQL As String

strSQL = "SELECT [tblTotal].[intCartID] FROM [tblTotal] WHERE ([tblTotal].[intCartID] = 0) "& _
"VALUES (@intCartID, @curGrandTotal)"

dparsons · February 18th, 2007, 12:04 AM

Ok a couple of things, first what is your VALUES statement for?? I am unfamiliar with a Values list being in a SELECT statement?

Unfortunatley your using access else I would suggest just writing a stored procedure to handle this and keep your code clean. I have a question though, wont your SELECT statement ALWAYS insert a new row? Your where clause doesnt evaluate against a variable, it always will evaluate against 0 and, by your explination, 0 means that the row doesn't exist hence a new row would be inserted.

In any case I would do something like SELECT Count(intCartID) as cartID from table where intcartid = 0

If Convert.ToInt32(dt.rows(0).item("cartID")) = n then
'execute insert statement
end if

Where n in the above statement will be how many rows are returned where the cartID = 0. (I assume it would be 0 as well but am not sure.)

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Discussion:
http://p2p.wrox.com/topic.asp?TOPIC_ID=56429