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The Ultimate Duplicate Index Finder Expand / Collapse
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Posted Tuesday, August 5, 2008 11:16 AM


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Comments posted to this topic are about the item The Ultimate Duplicate Index Finder


Post #546938
Posted Monday, October 20, 2008 2:16 PM
Old Hand

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I am not sure I understand what is considered a duplicate index. It appears that if more than one index starts with the same field, that it is considered a duplicate index. I have 4 indexes on one table that all have the same field as the first member. Why are these considered duplicate indexes?

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Glen
Post #588804
Posted Tuesday, October 28, 2008 11:21 AM


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It only outputs indexes that have common first seek columns. Indexes that have common first seek columns are dupes or might be merge-able, or the one of the indexes might be able to get their seek columns rearranged so you can have more index usage possibilities without adding more indexes.

I would only intentially have indexes with common first seek columns on tables with hardly any write activity.

The only other reason to dupe on first seek columns is to dupe on PKs that experience a lot of multi-row up-stream (from many to one; Where is on the many table) joins that cause bookmark lookups. PKs (also UQ constraints) can't have include columns, so you have to create another nonclustered index that has the seem seek as the PK and then add include columns.



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