From: Jonathan Gardner <jgardner@jonathangardner.net>
To: eVl One <evl@my-mail.com.ua>, Bruno Wolff III <bruno@wolff.to>
Subject: Re: How to check: is some key referenced from sometable
Date: Tue, 12 Aug 2003 09:46:54 -0700
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On Saturday 09 August 2003 14:44, eVl One wrote:
> So I need:
>    "silent delete" - i.e. when trying to DELETE row from A I'll not
> fall out with "$1 referential integrity violation - key in A still
> referenced from Bxx", but silently doesn't delete row ('cause run it
> from function and need function to executes farther after delete);
> "something to check reference" - system (potgresql) is very quickly
> realizes that key is referenced from another table, maybe this
> information may be accessed through some system relations, or so?
> Thanx for attention.

You may want to check out the "ON DELETE" and "ON UPDATE" clauses of the=20
FOREIGN KEY syntax. This will help you keep you data consistent.

Otherwise, if you want to know what is referencing something, you'll=20
have to query all of those tables. Your database structure should be=20
well-defined and thought out, so you should be able to figure out what=20
all is referencing it. If you need it for day-to-day queries, you may=20
want to rethink your design.

If you like, take a look at the pg_trigger table. The way PostgreSQL=20
manages the foreign key references is through triggers. You may be able=20
to identify which triggers are which, and from there, determine which=20
tables are referencing which tables.

- --=20
Jonathan Gardner <jgardner@jonathangardner.net>
Live Free, Use Linux!
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