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indexes

anish jain
Ranch Hand

Joined: Feb 03, 2010
Posts: 129
Please explain how does the index work in database?
Janeice DelVecchio
Saloon Keeper

Joined: Sep 14, 2009
Posts: 1789
    
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The index in a database works in the same way an index would work in a book. It's a way for the DB to retrieve data faster.

In Oracle you can make your own indexes for columns you use a lot, but some are made automatically for columns with Primary Key constraints or Unique constraints.


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anish jain
Ranch Hand

Joined: Feb 03, 2010
Posts: 129
Janeice DelVecchio wrote:The index in a database works in the same way an index would work in a book. It's a way for the DB to retrieve data faster.

In Oracle you can make your own indexes for columns you use a lot, but some are made automatically for columns with Primary Key constraints or Unique constraints.


Can you please elaborate? I want to know how does that work when someone fires a select query?
Tom Reilly
Rancher

Joined: Jun 01, 2010
Posts: 618
Can you please elaborate? I want to know how does that work when someone fires a select query?


Every database implementation is different. Here's a link that explains how Oracle database does it: http://www.dba-oracle.com/art_9i_indexing.htm
 
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