From: Jim Rowan <jmr@computing.com>
To: pgsql-sql@hub.org
Subject: WHERE clause?
Date: Wed, 14 Jul 1999 00:17:12 -0500
Message-ID: <199907140517.AAA23407@zee.computing.com> (raw)
In-Reply-To: <199907140300.XAA36099@hub.org>
I'm trying to create a log table to track changes to a table.. so I've
created a set of rules that look something like this:
CREATE RULE "m_log_change" AS ON UPDATE TO "machine"
do (
INSERT INTO machine_log (who, date, machnum, col, newval)
SELECT getpgusername(), 'now'::text, old.machnum,
'host', new.host
WHERE (new.host != old.host) or
(old.host IS NOT NULL and new.host IS NULL) or
(old.host IS NULL and new.host IS NOT NULL);
... more similar INSERT statements with different WHERE clauses..
);
My question is:
Is this the best way to code the WHERE? What I'm really after is "did the
value change?". I found that the tests to see if one-but-not-both of the
values is NULL are required to identify times when the value changed to or
from NULL.
Seems like a lot of extra work...
Jim Rowan DCSI DCE/DFS/Sysadmin Consulting
jmr@computing.com (512) 374-1143
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To: pgsql-sql@postgresql.org
Cc: jmr@computing.com, pgsql-sql@hub.org
Subject: Re: WHERE clause?
In-Reply-To: <199907140517.AAA23407@zee.computing.com>
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