Printed 2017/08/24 01:31AM

If Exists (Select 1...) vs If Exists (select * ...)

By Andy Warren, 2007/10/30

If exists is a well known way to improve performance because it returns as soon as it matches a single row - at that point it knows the condition is true and there is no need to continue.During a recent meeting guest speaker Bill Graziano mentioned that he uses if exists (select 1) instead of if exists (select *) as a performance optimization. Discussion revealed that this was based on a conversation with a MS person at some point, but Bill didn't have online URL to support it. Note that I'm not knocking Bill here, just curious to see if anyone can shed any light on this.
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