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jung1975
Aged Yak Warrior
503 Posts |
 Posted - 2005-10-20 : 13:25:56
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| I am not sure why SQL server is still using a Bookmark look up even though the proper indexes are placed in all of the columns where JOIN and WHERE clause are.How can I get rid of the Bookmark Lookup? |
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eyechart
Master Smack Fu Yak Hacker
3575 Posts |
Posted - 2005-10-20 : 13:33:37
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| the bookmark lookup occurs when you have a non-clustered index seek and the data you need is not contained in the index. It uses this to fetch the needed data from the corresponding table or clustered index (by row id or clustered index key).You can eliminate this by using a clustered index instead, or by using a covered index. A covered index is one that contains all the columns needed to satisfy the query. In a large query returning many columns that is not advisable, but for certain queries a covered index is a good choice. Sometimes the bookmark lookup is unavoidable because you already have a clustered index on your table (only one per table) or this particular index is not a good candidate for a clustered index (the cluster key is a GUID for example)-ec |
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jung1975
Aged Yak Warrior
503 Posts |
Posted - 2005-10-20 : 14:28:27
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| Thanks! EC |
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Bookmark Lookup in Excution Plan