Question

I have a stored procedure with a select and an update. I would like to prevent multiple users, from executing it, at the same time, so I don’t update, based on an incorrect select.
How do I lock it?
I’ve read various solutions (Transaction isolation, xlock), but I haven’t been able to figure what I really want, and how to do it.

Answer 1

The easiest way is to forget about data locks but look at sp_getapplock to control access through the code

BEGIN TRY

   EXEC sp_getapplock ...

   SELECT ...

   UPDATE ...

   EXEC sp_releaseapplock 

END TRY
...

Saying that, with thing like the OUTPUT clause and judicious use of ROWLOCK, UPDLOCK there is a good chance the UPDATE and SELECT can be one statement