SQL where sequence

[rib742]

I'm in the process of switching over to building pass thorough SQL queries in Access to run reports faster and wanted to know if the sequence of "where" makes a difference in the performance. For instance, if I change the sequence of the search criteria, will this possibly make the query run any faster?

 

[r937]

possibly

but in most relational database systems (note: you did not specify which one you're passing through to) it doesn't matter

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[r937]

oops, my bad, i stupidly overlooked the fact that you posted in the sql server forum, so it's safe to assume you're passing through to sql server

no, the sql server optimizer will figure out the fastest path, no matter what order you specify the WHERE conditions in

 

[rib742]

Thanks r937!

Just wanted to make sure before I go converting a lot of big queries.

 

[bboffin]

However SQL will try to make use of any indexes that you have set up in order to optimize the query so it's a good idea to create some useful indexes especially if the queries examine a lot of data and/or are run frequently.

SQL Query Analyzer will analyze your query and draw you a picture of its execution plan. This can reveal bottlenecks in queries.


Bob Boffin