SQL Server Central is supported by Red Gate Software Ltd.

Home Articles Editorials Forums Scripts Blogs QotD Books SQL Jobs Training Authors About us Contact us Newsletters Advertise Write for us

It Depends

Browse by Tag : SQL Server,oPASS (RSS)

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

By Andy Warren in It Depends | 10-30-2007 6:56 PM | Categories: Filed under: oPASS, SQL Server

Rating: (not yet rated) Rate this |

Discuss | 869 Reads | 102 Reads in Last 30 Days |no comments

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 www.opass.org 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.

It Depends

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

Blog Roll

Featured Blogs