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Clustered vs. Nonclustered


Clustered vs. Nonclustered

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dob111283
dob111283
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I just finished learning about clustered and nonclustered indexes and I was wondering a few things since I doubt I fully grasp these concepts yet. With nonclustered indexes, you can make them convering indexes by adding filters and INCLUDE column to make them as efficient as clustered indexes, so why use clustered indexes? Or is it because you can only use one clustered index per table, that you need to use nonclustered indexes? Again, I just finished learning these concepts the past few days so I'm trying to fully understand them.
SQLRNNR
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Here are a few resources that would be of benefit to you in trying to learn about indexes

http://www.sqlservercentral.com/stairway/72399/

And
http://www.sqlservercentral.com/articles/Indexing/68439/



Jason AKA CirqueDeSQLeil
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MCM SQL Server, MVP


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Posting Performance Based Questions - Gail Shaw

dob111283
dob111283
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Oh wow thanks for those links.
SQLRNNR
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You're welcome.



Jason AKA CirqueDeSQLeil
I have given a name to my pain...
MCM SQL Server, MVP


SQL RNNR

Posting Performance Based Questions - Gail Shaw

dob111283
dob111283
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While we are on the topic, "seek" and "lookup" seem like the same thing, at least in terms of their syntax and what they're trying to accomplish. I'm assuming with a seek, you can do multiple rows where with a lookup you can only do one row/column.
GilaMonster
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http://www.sqlservercentral.com/articles/Indexing/68439/
http://www.sqlservercentral.com/articles/Indexing/68563/
http://www.sqlservercentral.com/articles/Indexing/68636/
http://sqlinthewild.co.za/index.php/category/sql-server/indexes/


Seek - navigation down the b-tree of an index to locate a row or the start or end of a range of rows.
Lookup - single-row seek on the clustered index to fetch the rest of the columns necessary for the query.


Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

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