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hey001us
Posting Yak Master
185 Posts |
 Posted - 2007-05-10 : 21:42:31
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| Can any one explain about covering index and how to use that?hey |
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dinakar
Master Smack Fu Yak Hacker
2507 Posts |
Posted - 2007-05-10 : 21:47:28
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| http://www.sql-server-performance.com/covering_indexes.asphttp://www.mssqlcity.com/Tips/tipInd.htmand ofcourse books on line too.Dinakar NethiSQL Server MVP************************Life is short. Enjoy it.************************http://weblogs.sqlteam.com/dinakar/ |
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hey001us
Posting Yak Master
185 Posts |
Posted - 2007-05-10 : 21:57:12
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| Thx Dinakar. I posted this one I read that article, but I don’t know how to use.hey |
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hey001us
Posting Yak Master
185 Posts |
Posted - 2007-05-10 : 22:06:06
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| SELECT * FROM tblTaskProcesses (INDEX = IX_ProcessID) WHERE nextprocess = 1 AND processid IN (8,32,45)Is that above way I need to use? Then IX_ProcessID will be created automatically or do I need to create?hey |
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dinakar
Master Smack Fu Yak Hacker
2507 Posts |
Posted - 2007-05-11 : 01:17:01
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| What you have is an index hint. You are yelling at SQL server to use the Index you specify, even if there are better indexes available.No, you need to create the index inorder to use it. Covering index is including additional columns to an index to "cover" it. Sometimes you have columns that are not index worthy by themselves, as in they dont have enough distribution, like a status column. So you piggy back these columns along with other indexes. You cant just add any column to any index. It should make sense. From the links I posted:------A covering index, which is a form of a composite index, includes all of the columns referenced in SELECT, JOIN, and WHERE clauses of a query. Because of this, the index contains the data you are looking for and SQL Server doesn't have to look up the actual data in the table, reducing logical and/or physical I/O, and boosting performance.--------Dinakar NethiSQL Server MVP************************Life is short. Enjoy it.************************http://weblogs.sqlteam.com/dinakar/ |
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hey001us
Posting Yak Master
185 Posts |
Posted - 2007-05-23 : 17:10:04
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| Thank you for your explaination. Cheershey |
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covering index