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@postgresql.org [mailto:pgsql-general-owner@postgresql.org] On Behalf Of Steve Clark
Sent: Thursday, June 2, 2016 9:56 AM
To: pgsql <pgsql-general@postgresql.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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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@postgresql.org [mailto:pgsql-general-owner@postgresql.org] On Behalf Of Dann Corbit
Sent: Thursday, June 2, 2016 1:08 PM
To: 'Steve Clark' <steve.clark@netwolves.com>; pgsql <pgsql-general@postgresql.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@postgresql.org [mailto:pgsql-general-owner@postgresql.org] On Behalf Of Steve Clark
Sent: Thursday, June 2, 2016 9:56 AM
To: pgsql <pgsql-general@postgresql.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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http://www.postgresql.org/mailpref/pgsql-general

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On 06/02/2016 04:07 PM, Dann Corbit wrote:

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@postgresql.org [mailto:pgsql-general-owner@postgresql.org] On Behalf Of Steve Clark
Sent: Thursday, June 2, 2016 9:56 AM
To: pgsql <pgsql-general@postgresql.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

Hi Dan,

Thanks for the response - but I think that would give me id=6 and not id=3.

--
Stephen Clark

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​

-----Original Message-----
From: pgsql-general-owner@postgresql.org [mailto:
pgsql-general-owner@postgresql.org] On Behalf Of Steve Clark
Sent: Thursday, June 2, 2016 9:56 AM
To: pgsql <pgsql-general@postgresql.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.

On Thu, Jun 2, 2016 at 4:07 PM, Dann Corbit <DCorbit@connx.com> wrote:

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.