If ref_id is an instance of id and you are trying to filter that out, then use a self join -----Original Message----- From: pgsql-general-owner@xxxxxxxxxxxxxx [mailto:pgsql-general-owner@xxxxxxxxxxxxxx] On Behalf Of Dann Corbit Sent: Thursday, June 2, 2016 1:08 PM To: 'Steve Clark' <steve.clark@xxxxxxxxxxxxx>; pgsql <pgsql-general@xxxxxxxxxxxxxx> Subject: Re: dumb question This is your request, translated directly into SQL select max(id) from sometable where sts=0 and ref_id IS NULL Looking at your sample, it seems that sts is always 1 when ref_id exists, so it may possibly simplify to: select max(id) from sometable where sts=0 -----Original Message----- From: pgsql-general-owner@xxxxxxxxxxxxxx [mailto:pgsql-general-owner@xxxxxxxxxxxxxx] On Behalf Of Steve Clark Sent: Thursday, June 2, 2016 9:56 AM To: pgsql <pgsql-general@xxxxxxxxxxxxxx> Subject: dumb question Hi List, I am a noob trying to do something that seems like it should be easy but I can't figure it out. I have a table like so: id | ref_id | sts ------------------ 1 | | 0 2 | 1 | 1 3 | | 0 4 | | 0 5 | 4 | 1 6 | | 0 7 | 6 | 1 I want to find the max(id) whose sts is 0 but whose id is not referenced by ref_id. so the answer would be id=3. Thanks for any pointers, Steve -- -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
