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sushma patle
Starting Member
15 Posts |
 Posted - 2008-05-22 : 05:31:00
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| clustered index scan/seekwhat the meaning of that in estimated execution plan.and when we made any non clustered index then SQL server give what the name to it in display extimated execution plan.please give me answerspatle |
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harsh_athalye
Master Smack Fu Yak Hacker
5581 Posts |
Posted - 2008-05-22 : 05:42:47
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| From Books Online:Clustered Index ScanThe Clustered Index Scan logical and physical operator scans the clustered index specified in the Argument column. When an optional WHERE:() predicate is present, only those rows that satisfy the predicate are returned. If the Argument column contains the ORDERED clause, the query processor has requested that the rows' output be returned in the order in which the clustered index has sorted them. If the ORDERED clause is not present, the storage engine will scan the index in the optimal way (not guaranteeing the output to be sorted).Clustered Index SeekThe Clustered Index Seek logical and physical operator uses the seeking ability of indexes to retrieve rows from a clustered index.The Argument column contains the name of the clustered index being used and the SEEK:() predicate. The storage engine uses the index to process only those rows that satisfy this SEEK:() predicate. It optionally can include a WHERE:() predicate, which the storage engine evaluates against all rows satisfying the SEEK:() predicate (it does not use indexes to do this).If the Argument column contains the ORDERED clause, the query processor has determined that the rows must be returned in the order in which the clustered index has sorted them. If the ORDERED clause is not present, the storage engine searches the index in the optimal way (not guaranteeing the output to be sorted). Allowing the output to retain its ordering can be less efficient than producing nonsorted output.as to your second question,SQL Server displays actual name of NC index in estimated execution plan.Harsh AthalyeIndia."The IMPOSSIBLE is often UNTRIED" |
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rmiao
Master Smack Fu Yak Hacker
7266 Posts |
Posted - 2008-05-22 : 23:15:57
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| And clustered index scan basically is table scan. |
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