peter-757102 (2/10/2010)

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CraigIW (2/10/2010)

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nicholasw (2/10/2010)

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Instead of:

IF EXISTS(SELECT 1 FROM ......WHERE....)

Would the following be quicker still?

IF EXISTS(SELECT TOP 1 1 FROM ......WHERE....)

No, as the "top 1" is only done after the "select 1 from".

Funny enaugh, it is not always that simple. I seen cases where a:

select top 1 max(id)

outperformed

select max(id)

many times over, and I suspect top sometimes acts as a undocumented hint. I got some testing to do on it still, and if it pans out it might also be a trick to control table variables bestter by using top to provide an estimate other then the constant 1 and thus get better query plans.