Date: Sun, 1 Feb 2004 06:34:51 -0700
From: Michael Fuhr <mike@fuhr.org>
To: darnold@northcoast.com
Cc: pgsql-sql@postgresql.org
Subject: Re: An order by question
Message-ID: <20040201133451.GA13002@winnie.fuhr.org>
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> I need a little help on a sorting problem. Imagine a table, call it
> records, that has fields:
> 
> lastName
> firstName
> term
> 
> I want to sort the records by last name, then first name, and finally by
> term. This almost does what I want:
> 
> select * from records order by lastName, firstName, term;
> 
> However, the possible values for term are:
> 
> 2002F
> 2003S
> 2003X
> 2003F
> 
> Where F is for fall, S for spring, and X for summer session. Thus, a
> straight alphabetical sort doesn't give me what I want. If the year is the
> same, then I want a sort with S, then X, then F for identical year.

Consider storing the session in a separate field and assigning each
session a value that collates in the order you want.

Here's a way to order the sessions using their current format:

SELECT *
FROM records
ORDER BY lastName,
         firstName,
         SUBSTRING(term FROM 1 FOR 4),
         CASE SUBSTRING(term FROM 5)
           WHEN 'S' THEN 1
           WHEN 'X' THEN 2
           ELSE 3
         END;

-- 
Michael Fuhr
http://www.fuhr.org/~mfuhr/