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Discuss content posted by Gail Shaw
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Introduction to Indexes
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Introduction to Indexes
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e-ghetto
e-ghetto
Posted Wednesday, July 04, 2012 2:05 AM
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GilaMonster (7/4/2012)
For seeking, for range scans, for supporting an order by.
Oh, I didn't have the ORDER BY clause in mind yet. Thanks, it's more clearly now.
So, if I my query returns the records in the descending order - it is better to create the index column also in the same order ("DESC"), right?
Post #1324849
paul.knibbs
paul.knibbs
Posted Wednesday, July 04, 2012 2:08 AM
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GilaMonster (7/4/2012)
For seeking, for range scans, for supporting an order by. Not ever for returning rows in the index order without an order by specified. That was quoted a bit out of context (context being ordering of returned rows without an order by)
Would it potentially make a difference to the amount of fragmentation caused by adding new items to the index? e.g. if your index key is a value that will generally *decrease*, would you get a less fragmented index by declaring it DESC?
Post #1324851
GilaMonster
GilaMonster
Posted Wednesday, July 04, 2012 2:15 AM
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Maybe. Will it be a big difference and will the reduction in fragmentation affect query performance? Depends on other factors (frequency of inserts, type of queries, etc)
Gail Shaw
Microsoft Certified Master: SQL Server 2008, MVP
SQL In The Wild
: Discussions on DB performance with occasional diversions into recoverability
We walk in the dark places no others will enter
We stand on the bridge and no one may pass
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