>Sergey,
>
>That's helpful. Could you please explain one simple principle on this example:
>

>IF @tcUserID IS NULL
>      BEGIN
>        PRINT 'ERROR: The UserID value must contain a value.'
>        RETURN 1
>      END
>

>What happens here? Is it an early exit point?

Yes

>Do I need to enclose IF with ELSE always?

No.

>
>I want to understand the principle, I looked into few SPs and I'm trying to read Help, but it's not that helpful so far... May be I'm looking in the wrong place...
>