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Using Indexing concept for performance ?

RaviNada Kiran
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Joined: Jan 30, 2009
Posts: 528
Hi Ranchers ,

Is Indexing on a Database column is performed dynamically depending on the search parameters selected by the user? Or at the time of table creation ??

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steve souza
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Joined: Jun 26, 2002
Posts: 861
I can't speak for all databases, but in Sybase the query optimizer looks at the arguments passed to a query and determines the best available index or none at all based on which one it thinks will perform best at the time of the query.


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RaviNada Kiran
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Joined: Jan 30, 2009
Posts: 528
can you describe , How can i write a SQL Query which performs dynamic indexing of a database column??
Anurag Blore
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Joined: Jan 15, 2003
Posts: 74
Ravi,

I am not sure if youcan write a SQL which will create indexing on a table. You shuold create index on a table based on your requirement. Creating indexing on all the columns could have performance impact.

You can refer here for basic indexing conepts
sql indexing


Thanks,
Anurag
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RaviNada Kiran
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Joined: Jan 30, 2009
Posts: 528
Anurag Blore wrote:Ravi,

I am not sure if youcan write a SQL which will create indexing on a table. You shuold create index on a table based on your requirement. Creating indexing on all the columns could have performance impact.

You can refer here for basic indexing conepts
sql indexing




Thanks a lot.
Tim Holloway
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Joined: Jun 25, 2001
Posts: 16020
    
  20

Indexing isn't actually defined by the SQL standard, which is based on abstract data access without regard to the limitations of the real world. Some DBMS's may index on their own initiative, but most commonly it's explicitly done via DDL.

Indexing can greatly speed performance, but it can also do the reverse. A classic example is to do a bulk load for an indexed table. Because the index trees are usually being rebalanced with each record loaded, this can make a load take an excruciatingly long long time. Instead, the common procedure is to load an unindexed table, then index it. That's actually a practice that predates DBMS's as we know them.

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RaviNada Kiran
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Joined: Jan 30, 2009
Posts: 528
Tim Holloway wrote:
Indexing can greatly speed performance, but it can also do the reverse. A classic example is to do a bulk load for an indexed table. Because the index trees are usually being rebalanced with each record loaded, this can make a load take an excruciatingly long long time.


Great point . Thank you very much
 
 
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