To: "Alfred" <99m@myway.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Tough Problem -- Record Checkouts
References: <1139851981.176833.302970@g43g2000cwa.googlegroups.com>
In-Reply-To: <1139851981.176833.302970@g43g2000cwa.googlegroups.com>
From: Greg Stark <gsstark@mit.edu>
Organization: The Emacs Conspiracy; member since 1992
Date: 18 Feb 2006 02:58:03 -0500
Message-ID: <87bqx514l0.fsf@stark.xeocode.com>
Lines: 30
User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.4
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii


"Alfred" <99m@myway.com> writes:

> CO    |     N
> ------+-----------------------
> 0     |     15-59
> 1     |     0, 16-59
> 2     |     0-1, 17-59
> 15    |     0-14, 30-59
> 16    |     0-15, 31-59
> 30    |     0-29, 45-59
> 31    |     0-30, 46-59
> 45    |     0-44
> 46    |     1-45
> 59    |     14-58
> 
> This becomes some kind of UPDATE statement with a complex WHERE clause.

That's usually a sign you're storing the data in the wrong form. Why are you
storing just the minutes and not the absolute timestamp of the checkout?

In any case the where clause isn't all that complex. I think you've confused
yourself by drawing the inverse table of what you need. You need the range of
CO to expire for a given N, not the range of N in which you should expire a
given CO.

WHERE co BETWEEN 0 AND n-15 OR co BETWEEN n+1 AND n+45

-- 
greg