Date: Tue, 26 Nov 2002 08:11:53 -0800 (PST)
From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: <nathan@ncyoung.com>
Cc: <pgsql-sql@postgresql.org>
Subject: Re: join question
In-Reply-To: <MHTPHEXXXSIELH1XSDBVSPOZYE9BA.3dde8914@inky>
Message-ID: <20021126080514.C77510-100000@megazone23.bigpanda.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII


On Fri, 22 Nov 2002, Nathan Young wrote:

> Hi all.
>
> I have a table with members and a table with payments.  Each payment is
> related to a member by memberID and each payment has (among other things) a
> year paid.
>
> I can create a join to find a list of members who have paid for a given year
> (2002 in this case):
>
> select member.memberID,member.name from member, payment where
> payment.memberID = member.memberID and payment.yearPaid = 2002
>
> I would like to be able to get a list of members who have not paid for a
> given year.

Well, I believe either of these two will do that:

 select member.memberId, member.name from member where not exists (select
  * from payment where payment.memberId=member.memberID and
  payment.yearPaid=2002);

 select member.memberId, member.name from member left outer join
  (select * from payment where yearPaid=2002) as a using (memberId) where
  yearPaid is null;

> I would also like to combine the two criteria, for example to generate a list
> of members who have paid for 2002 but not 2003.

I think these would do that:

select member.memberID,member.name from member, payment where
 payment.memberID = member.memberID and payment.yearPaid = 1999
 and not exists (select * from payment where
 payment.memberId=member.memberId and yearPaid=2002);

select member.memberId, member.name from member inner join (select
 * from payment where yearPaid=2002) as a using (memberId) left outer join
 (select * from payment where yearPaid=2003) as b using (memberId) where
 b.yearPaid is null;