Re: Need SQL Help Finding Current Status of members

From: Richard Huxton <dev(at)archonet(dot)com>
To: Michael Avila <Michael(dot)Avila(dot)1(at)sbcglobal(dot)net>
Cc: SQL PostgreSQL MailList <pgsql-sql(at)postgresql(dot)org>
Subject: Re: Need SQL Help Finding Current Status of members
Date: 2005-12-16 09:24:22
Message-ID: 43A287C6.2090501@archonet.com
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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

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