RE: Referential indexes

  • From: "Mercadante, Thomas F" <thomas.mercadante@xxxxxxxxxxxxxxxxx>
  • To: "'GLeonard@xxxxxxxxxxxxx'" <GLeonard@xxxxxxxxxxxxx>, oracle-l@xxxxxxxxxxxxx
  • Date: Fri, 28 Jan 2005 07:51:43 -0500


I agree with Nuno - developers are wrong.  As long as there is an index on
the child column (either PK or a non-unique index), then it does not matter.

As a test, have your friend try and create the additional index.  Oracle may
stop him/her saying that the column is already indexed.

If the index is created, run a simple explain plan against a query using the
child table.  The PK/unique index will *always* be used before the
non-unique index.

Good Luck!


-----Original Message-----
From: Leonard, George [mailto:GLeonard@xxxxxxxxxxxxx] 
Sent: Friday, January 28, 2005 4:51 AM
To: oracle-l@xxxxxxxxxxxxx
Cc: Desplace, Laura
Subject: Referential indexes

Hi all

Got this query from a developer, or actually they are actually arguing
with the DBA team.

Table A - master, acc number field              also only column in PK

Table B - Child, acc Number Field               acc number is the first
column in PK, PK contains 2 more columns.

DBA's are saying we don't need a normal non unique stand alone index on
the acc Number field for table B.

Developers want a separate index,


George Leonard
Oracle Database Administrator
New Dawn Technologies @ Wesbank
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