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amit_18706
Starting Member
1 Post |
 Posted - 2014-05-08 : 04:26:20
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| Hello,Recently one of our performance test was taking long time to run on the server and was getting timed out. When we applied "Select Distinct" to our query it started performing fine. Distinct generally removes duplicate records but query earlier was not returning any duplicate records either.Can anyone explain how "SELECT DISTINCT" improved performance bcoz it generally is an overhead on the DB server. Are there any exceptional cases where use of DISTINCT really benefits?Thanks |
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stepson
Aged Yak Warrior
545 Posts |
Posted - 2014-05-08 : 04:44:59
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| I think that cause/trigger a recompile of your sp and now , the query plan is optimized for the current statesabinWeb MCP |
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Ifor
Aged Yak Warrior
700 Posts |
Posted - 2014-05-08 : 05:43:10
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| Sometimes DISTINCT in a CTE/Derived table etc that then gets joined to something else can improve performance, if a lot of duplicates are removed, as the join/subquery has less to do. |
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Using SELECT DISTINCT in SQL SERVER 2008