From: | Lincoln Yeoh <lylyeoh(at)mecomb(dot)com> |
---|---|
To: | Mike Mascari <mascarm(at)mascari(dot)com> |
Cc: | pgsql-general(at)postgreSQL(dot)org |
Subject: | Re: [GENERAL] null and = |
Date: | 1999-12-06 07:00:10 |
Message-ID: | 3.0.5.32.19991206150010.008a9450@pop.mecomb.po.my |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-general |
At 10:39 PM 05-12-1999 -0500, Mike Mascari wrote:
>I would just do:
>
>SELECT users.usr_id, users.usr_login FROM users WHERE NOT EXISTS
> (SELECT wm_accounts.usr_id FROM wm_accounts WHERE
> wm_accounts.usr_id = users.usr_id);
OK, my current query is
select usr_id,usr_login from users where usr_id not in (select userid from
wm_accounts);
Your query on small test tables (after vacuum analyze):
Seq Scan on users (cost=1.83 rows=25 width=16)
SubPlan
-> Seq Scan on wm_accounts (cost=1.33 rows=2 width=4)
My query:
Seq Scan on users (cost=1.83 rows=25 width=16)
SubPlan
-> Seq Scan on wm_accounts (cost=1.33 rows=10 width=4)
What does rows mean? But it looks like your query is better :). Don't fully
understand why tho. Would it work if wm_accounts is empty?
>> I would prefer a query which can work if the second table is null. The
>> problem with other queries I thought of was they would return null if the
>> second table is null.
>>
>
>I'm not sure what you mean here. Do you mean the table doesn't exist, is
empty,
>or that the usr_id field is NULL?
I meant the table is empty.
>What happens if a record is added to wm_accounts? Do you want a record to
also
>be created in users as well, or is users a superset with respect to
wm_accounts
>and usr_id?
Users is a superset.
Thanks for your suggestion,
Link.
From | Date | Subject | |
---|---|---|---|
Next Message | Edouard DESSIOUX | 1999-12-06 09:19:32 | How to select where .... |
Previous Message | Madarasz Karoly | 1999-12-06 06:57:13 | database GUI library for C,C++ |