Re: dumb question

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(at)postgresql(dot)org [mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of Dann Corbit
Sent: Thursday, June 2, 2016 1:08 PM
To: 'Steve Clark' <steve(dot)clark(at)netwolves(dot)com>; pgsql <pgsql-general(at)postgresql(dot)org>
Subject: Re: [GENERAL] 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(at)postgresql(dot)org [mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of Steve Clark
Sent: Thursday, June 2, 2016 9:56 AM
To: pgsql <pgsql-general(at)postgresql(dot)org>
Subject: [GENERAL] 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

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