Stephany
Sat Nov 18 16:27:42 CST 2006
Close, but no cigar.
If the Jet OleDb handled named parameters a'la Sql Server then the generated
statement would look like this:
Me.OleDbUpdateCommand1.CommandText = "UPDATE Member_Listing SET address_1 =
@address_1, address_2 = @address_2 WHERE (member_ID = @Original_member_ID)
AND (address_1 = @Original_address1 OR @address_1 IS NULL AND address_1 IS
NULL) AND (address_2 = @Original_address_2 OR @address_2 IS NULL AND
address_2 IS NULL)
Because it doesn't, you have to consider which parameter is satisfying which
'?'.
The condition of the WHERE clause that deals with address_1 is making sure
that the row in the database is in the same state as when you populated your
dataset object and likewise for address_2. If it is not in the same state
then it means that the database row has been modified since you read it and
the UPDATE will fail. This is a technique called 'optimistic concurrency'
which means that rows are not locked for editing and can be modified by
other users or processes at any time and it is used to avoid new data being
overwritten.
"Dave" <dls5678@community.nospam> wrote in message
news:ujMXFdyCHHA.204@TK2MSFTNGP04.phx.gbl...
>I used the wizard in VB.NET 2003 to generate a data adapter and it created
>the following update command. It seems like the WHERE clause would never
>evaluate to true? Am I reading this wrong?
>
> The member_ID is the key for the table but it looks like the 2 statements
> checking the address_1 and address_2 values would only be true if no
> changes were made.
>
> Me.OleDbUpdateCommand1.CommandText = "UPDATE Member_Listing SET address_1
> = ?, address_2 = ? WHERE (member_ID = ?) AND (address_1 = ? OR ? IS NULL
> AND address_1 IS NULL) AND (address_2 = ? OR ? IS NULL AND address_2 IS
> NULL)
>
> Thanks for your help.
>
> Dave
>