Multiple indexes on a column

From: Brett May <bmay_at_blkbox.COM>
Date: 20 Feb 1994 00:36:52 -0600
Message-ID: <2k70e4$p5s_at_blkbox.blkbox.COM>

We are running oracle 7.0.15, and I am trying to balance indexes with disk space. My question:

We have a large table which has a primary key of 5 columns (say, a, b, c, d and e). When I define a primary key constraint over the table, my understanding is that a single concatenated index is created over all five columns. Is this correct? If so, is there any benefit to creating additional individual indexes over the same columns. For example, lets say I knew the users would be often doing something like: SELECT whatever FROM my_Table
WHERE a=something AND b=something_else;W

If I created another additional index over a and b alone, would it buy me anything? Or would the query get as much benefit from the original index of which a and b are only a part?

Just curious... please reply here or by e-mail if you know the answer. Thanx,
Brett

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Received on Sun Feb 20 1994 - 07:36:52 CET