Oracle-L: Re: relationship between unique index and constraint

From: Richard Foote <richard.foote_at_bigpond.com>
Date: Sat, 19 Apr 2003 16:41:39 -0800
Message-ID: <F001.0058577D.20030419164139@fatcity.com>

Hi Arup,

I might be mentioning the bleeden obvious here, but if the constraint is deferrable, Oracle will use a non-unique index to police the constraint. If a suitable non-unique index exists before a unique constraint is created, Oracle will simply use it.

Cheers

Richard

Original Message ----- To: Multiple recipients of list ORACLE-L Sent: Saturday, April 19, 2003 5:36 AM

David,

Here is the lowdown on the issue:

When you create a unique CONSTRAINT, Oracle creates a unique INDEX to enforce it.
When you create a unique INDEX, a constraint is NOT automatically created, but the rdbms engine reports the same message as if the constraint name was violated.

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Author: Richard Foote
INET: richard.foote_at_bigpond.com

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