Getting the MS SQL Identity ID With a Complex UPDATE / INSERT Statement

As I posted in my blog entry MSSQL Update/Insert Based Upon Existing Record, it is better to use “IF @@ROWCOUNT=0” rather than “IF EXISTS ()” when updating or inserting a record based upon existence. This is because the preferred method only does a table/index scan once, while the later will do it twice.

What if you need the Identity Column ID whether the record is updated or inserted? Normally in ColdFusion you can use “queryResult[“GENERATEDKEY”]”, however what you will find is this variable only works on simple insert statements. If you try to use @@IDENTITY or SCOPE_IDENTITY, you will find it only returns the Identity Column ID when the insert is triggered.

Introducing MS SQL’s OUTPUT clause, introduced in MS SQL 2005. We can use the OUTPUT clause to return the Identity Column ID(s).

When we add this to the INSERT and UPDATE clauses, the problem we run into is that during an insert it will return an empty set and another set containing the Identity Column ID that was inserted. Therefore we use a temporary table to help us with this.

Now with a temporary table, we introduce back in the second table scan. However this table scan will have very limited rows, if not just one. Plus the temporary table will not need disk access. So the second table scan is of no consequence.

So with all this in mind here’s an example that returns the Identity column that was either inserted or updated. Keep in mind that multiple IDs will be returned as separate rows if more than one table row was updated.

<cfquery name="local.qSetCart">			
	DECLARE @T TABLE (
	    cartID INT NOT NULL
	)
	
	UPDATE
		UserCart
	SET
		dateModified = GETDATE(),
		isGift = <cfqueryparam value="#arguments.isGift#" cfsqltype="cf_sql_bit">
	OUTPUT
		INSERTED.cartID INTO @T
	WHERE
		userID = <cfqueryparam value="#arguments.userID#" cfsqltype="cf_sql_integer">
	
	IF @@ROWCOUNT = 0
	
		INSERT
			INTO UserCart ( userID, isGift)
		OUTPUT
			INSERTED.cartID INTO @T
		VALUES (
			<cfqueryparam value="#arguments.userID#" cfsqltype="cf_sql_integer">,
			<cfqueryparam value="#arguments.isGift#" cfsqltype="cf_sql_bit">
		)
	
	SELECT cartID FROM @T
</cfquery>
		
<cfreturn local.qSetCart.cartID>
Advertisements

#coldfusion-2, #identity, #sql

“Element GENERATEDKEY is undefined…” after ColdFusion SQL Statement

This is a followup post to “Returning IDENTITY ID via ColdFusion 9′s CFQuery“.

Today I created an Insert statement that I needed the new identity value returned. It’s pretty simple, calling the result.generatedkey as such:

<cfquery result="myResult">
    INSERT INTO users( username )
    VALUES( 'test' )
</cfquery>
<cfreturn myResult["GENERATEDKEY"]>

The above code would normally result in the new identity value created for that record. However I received a “GENERATEDKEY is undefined…” error. Not sure what to think I dumped out the myResult variable, put the query into a file of itself and even tried using myResult.IDENTITY instead to no avail. After taking awhile figuring this out and ended up going home for the day and trying there again after a couple of hours. All of a sudden the standalone test worked!

So I’m thinking, okay this has to be some setting somewhere, and I was right. I narrowed it down to a query that runs before it during the login process for my website.

SET NOCOUNT ON

UPDATE TABLE1
SET COL1 = 'myVal'

Notice that I didn’t set “SET NOCOUNT OFF”. There lies the issue. Apparently when you set NOCOUNT off and keep it off, ColdFusion doesn’t retrieve the new Identity value. So the following code fixed my issue:

SET NOCOUNT ON

UPDATE TABLE1
SET COL1 = 'myVal'

SET NOCOUNT OFF

#cfquery, #coldfusion-2, #generatedkey, #identity, #nocount, #sql