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Re: How is "UNION ALL " work in ORACLE ?

From: Christopher M. Day <christopher.day_at_rdbms.freeserve.co.uk>
Date: Fri, 29 Jan 1999 19:31:10 +0000
Message-ID: <36B20C7E.91833A58@rdbms.freeserve.co.uk>


Hi,

We have similar sized tables that we need to apply set operators to. The performance of multiple set operators can be terrible.

Our workaround was to create temporary tables using the UNRECOVERABLE or NOLOGGING PCTFREE 0 and PCTUSED 99 clause from each select statement. The apply the set operations to these temporary tables !

The performance improvement is amazing for large tables.

Chris.

yewpc_at_my-dejanews.com wrote:
>
>
> What I want is to improve the performance. Currently the txn_code is indexed
> and it may have up to 300 rows of same the value out of 50 millions records.
>
> Anyone have any idea or suggestion ?
>
> Thank you very much .
>
> -----------== Posted via Deja News, The Discussion Network ==----------
> http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own
Received on Fri Jan 29 1999 - 13:31:10 CST

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