Re: An order by question

From: Michael Fuhr <mike(at)fuhr(dot)org>
To: darnold(at)northcoast(dot)com
Cc: pgsql-sql(at)postgresql(dot)org
Subject: Re: An order by question
Date: 2004-02-01 13:34:51
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/

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