Which of these is faster? 1

[StoneDeCroze]

Hi Guys,
Anyone know whis of these will be faster:
@ASWN is a DECIMAL(18,6)
@ID is an INT

IF @ASWN > 0
UPDATE table SET field1=@ASWN WHERE ID=@ID

or

UPDATE table SET field1=@ASWN WHERE ID=@ID AND @ASWN > 0

Logically they are the same:
The first results in the execution of one or two statements, the second only ever one.
However, will the second example always look up ID in table, or if @ASWN <= 0 will it not bother (and is therefore probably quicker).

Thanks for any insights
Peter

 

[vongrunt]

First case is better, both semantically and performance-wise.

Semantically because code is more readable - and because @ASWN is a constant during query's lifetime.

Performance-wise - because in 2nd example optimizer may apply Filter operator after the rest of WHERE clause. Even if it doesn't do that, 1st case is marginally faster.

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