December 17, 2004 at 9:48 am
I’ve got a unique question for those of you that might be "gurus" concerning SQL Server:
Does anyone have definite proof of a performance difference between using Equi-Joins (joins that happen in the where clause) compared to Inner/Outer Joins? (Notice I grouped Inner and Outer Joins together against the Equi-joins for this discussion)
For smaller record sets, I know the performance boost would be infinitesimal. For larger queries where 8+ tables are being joined and returning 2500+ record sets, any performance boost we can get would help us to lessen the load on the SQL Server not to mention make our clients happy.
I know that in SQL Server 7, there was a performance boost – but since the precompiler in SQL Server 2K changed considerably, was this performance boost lost or is it still in effect (or shall I dare say expanded on)?
Any definitive proof someone has would be appreciated.
December 17, 2004 at 12:25 pm
There is another topic here
http://www.sqlservercentral.com/forums/shwmessage.aspx?forumid=8&messageid=151303
where the persons states a join in the where is coming out faster than a true joined query.
However at worst case they should perform the same as the query engine will a lot of times restate the query internally into the joins from the whered condition.
I from expeirence would say it depeneds on the data, indexes and how the query is written. But in essence writing
SELECT * FROM tblA, tblB WHERE tablA.col1 = tblB.col1
will get restated by the query engine as
SELECT * FROM tblA INNER JOIN tblB ON tablA.col1 = tblB.col1
anyway.
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