Interesting. I think I understand that. I have never worked with a SELECT within a SELECT (I think that is called a subquery). I am guessing that it works its way through the member status records until the latest date "floats" to the top (nothing is > than it).
Will that be a problem performance-wise if there are thousands of records? Thanks for the help. Mike > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Patrick JACQUOT > Sent: Friday, December 16, 2005 5:12 AM > Cc: SQL PostgreSQL MailList > Subject: Re: [SQL] Need SQL Help Finding Current Status of members > > > Richard Huxton wrote: > > > 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. > > There is a standard way : > > Select * from memberstatus A where not exists > (select * from emberstatus B where B.member_id=A.member_id and > B.status_date >A.status_date) > > ---------------------------(end of broadcast)--------------------------- > TIP 5: don't forget to increase your free space map settings ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
