Detecting dirty reads from a stored procedure

Question

I\'ve got 100 threads that are each calling the stored procedure as defined below.

How do I prevent dirty reads?

SET QUOTED_IDENTIFIER OFF
SET ANSI_NULLS         


        

Answer 1

If you need to update and return what you updated, then I would just use the OUTPUT clause:

UPDATE CfgCerealNumber 
SET CerealNumber = CerealNumber + 1 
OUTPUT INSERTED.CerealNumber
WHERE CerealNumberID = @TableID;

If you need additional checking, you can OUTPUT into a declared table variable before returning the result set from the stored procedure.

Another alternative would be to create a blocking lock on the table first, and then update:

SELECT @CerealNumber = CerealNumber + 1 
FROM CfgCerealNumber WITH (HOLDLOCK, UPDLOCK) 
WHERE CerealNumberID = @TableID;

UPDATE CfgCerealNumber
SET CerealNumber = @CerealNumber
WHERE CerealNumberID = @TableID;

But I would put money down that I've seen this still cause problems. I trust it much less.