-----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.
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
Please don't top-post.
Your query would select "id=6", which is disqualified due to id=7...
For the record one reads: "whose id is not referenced by ref_id" AS "id NOT IN (ref_ids....)"; ref_id IS NULL means "that lacks a ref_id" and is evaluated independent of the id.
David J.
