Re: foreign key: auto-index creation?

From: Mark D Powell <mark.powellNOmaSPAM_at_eds.com.invalid>
Date: 2000/07/24
Message-ID: <0d314428.8466c244@usw-ex0102-015.remarq.com>#1/1

Randall Parker <rgparker_at_west.net> wrote:
>I've been told that Sybase ASA automatically creates an index
in the
>referring table for all declared foreign key constraints. Does
Oracle do
>likewise?
>
>DB2 and MS SQL Server both require explicit creation of indexes
to
>support foreign keys. I'm wondering if Oracle is more like them.
>
>

Oracle requires the DBA/Developer to explicitly create indexes on FK columns in the referencing table. The main reason for this is that in a large number of these cases the index on the FK columns is unnecessary. However, there are many cases where the index is needed so it is necessary to consider update activity on the referenced table whenever a FK is declared and to make a conscious decision to build the index or not.

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