Date: Wed, 31 Jul 2002 16:17:04 -0700 (PDT)
From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: Tom Haddon <tom@betterhealthfoundation.org>
Cc: <pgsql-sql@postgresql.org>
Subject: Re: Case Statement
In-Reply-To: <NEBBIHDGCLBEJMPFAMLAGEKCCHAA.tom@betterhealthfoundation.org>
Message-ID: <20020731160809.M21990-100000@megazone23.bigpanda.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII

On Wed, 31 Jul 2002, Tom Haddon wrote:

> Hi Folks,
>
> Pretty basic one here. I'm trying to do a SELECT statement that includes a
> CASE structure that will be used in the ORDER BY clause, and I want the CASE
> structure to evaluate a bunch of criteria and in each case increment its
> value by a certain amount:
>
> SELECT id, description CASE
> 		field1 IS TRUE THEN CASE=CASE+1
> 		field2 IS TRUE THEN CASE=CASE+2
> 		END
> FROM table
> ORDER BY CASE, description;
>
> Am I misunderstanding what CASE can do here, and if so, how else do I do
> what I'm trying to do? I know that that isn't right - any pointers
> appreciated.

Are you trying to get a 0-3 based on field1 and field2 or some kind of
aggregate?  The first you can do that with something like
 case when field1 is true then 1 else 0 end +
 case when field2 is true then 2 else 0 end
I think. (Extend for more columns)

Or if you've got like 7-8 columns maybe just make a function that does
the work for you for clarity.

You'll also need a comma after description and you'll want to alias the
case expression and use that in order by or use the position number.