DISTINCT vs GROUP BY

[mbabcock]

Assuming an index on cCustNum field, which would be better in terms of performance?

1) select distinct cCustNum from MyTable where <somecondition>

2) select cCustNum from MyTable where <somecondition> GROUP BY cCustNum

QA's estimated execution plan seems to show that these are identical, but I thought I had heard some time ago that GROUP BY was optimizable moreso that DISTINCT.

BOL seems to give no clear indication when I searched.

tia!
--Michael

 

[mrdenny]

With an index on the column they should perform the same.

Denny
MCSA (2003) / MCDBA (SQL 2000) / MCTS (SQL 2005) / MCITP Database Administrator (SQL 2005)

--Anything is possible. All it takes is a little research. (Me)

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