Message-ID: <43A287C6.2090501@archonet.com>
Date: Fri, 16 Dec 2005 09:24:22 +0000
From: Richard Huxton <dev@archonet.com>
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To: Michael Avila <Michael.Avila.1@sbcglobal.net>
Cc: SQL PostgreSQL MailList <pgsql-sql@postgresql.org>
Subject: Re: Need SQL Help Finding Current Status of members
References: <NBBBLNPHAMCFENDFHIDCGENBEGAA.Michael.Avila.1@sbcglobal.net>
In-Reply-To: <NBBBLNPHAMCFENDFHIDCGENBEGAA.Michael.Avila.1@sbcglobal.net>
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Michael Avila wrote:
> I have a table which keeps track of the status of members. In the table is 
> 
> 
> member_id int(8)
> status_code char(1)
> status_date date 
> 
> KEY member_id (member_id,status_code,status_date)
> 
> 
> Each member can have multiple records because a record is added each time
> the status changes but the old record is kept for history.
> 
> What I want to do is find the latest status for each member.

Michael Fuhr has already described on solution, but if you can alter the 
table definition then there might be a neater solution.

Replace "status_date" with "status_expires" and make it a "timestamp 
with time zone". Set the expiry to 'infinity' for the current record and 
  you then have a simple select to find the most recent.

If you regularly want to find which record was active on a particular 
time you'll want two columns: valid_from and valid_to. This makes it 
much easier to find a row for a specific date.
-- 
   Richard Huxton
   Archonet Ltd