| Re: Searching performance [message #51301] |
Tue, 14 May 2002 13:59 |
andrew again
Messages: 2577
Registered: March 2000
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Senior Member |
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Placing the most selective columns first in an index has been shown to be a myth (I used to believe it too), actually having the less selective columns first allows effective use of the compress option during index creation.
"large" tables are sypically many millions of rows.
The aim is to try to avoid full table (or partition) scans if the amount of rows matching your query criteria is low (say 0-20% max. this % depends on row length to some extent and block size). Try to avoid a pl/sql solution and try to do it in sql.
Run explain plan on your update/query statement.
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