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Re: subquery/alias question

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Michael Glaesemann wrote:
>
> On Sep 25, 2007, at 16:59 , Madison Kelly wrote:
>
>> SELECT
>> 	d.dom_id,
>> 	d.dom_name,
>> 	(SELECT COUNT(*) FROM users u WHERE u.usr_dom_id=d.dom_id)
>> 	AS
>> 	usr_count
>> FROM
>> 	domains d
>> WHERE
>> 	(SELECT COUNT(*) FROM users u WHERE u.usr_dom_id=d.dom_id) > 0
>> ORDER BY d.dom_name ASC;
>
> Why not just use a join? Something like this would work, I should think:
>
> select dom_id,
>        dom_name,
>        usr_count
>   from domains
>   natural join (select usr_dom_id as dom_id,
>                        count(usr_dom_id) as usr_count
>                   from users) u
>   where usr_count > 0
>   order by dom_name;

Maybe the usr_count should be tested in a HAVING clause instead of
WHERE?  And put the count(*) in the result list instead of a subselect.
That feels more natural to me anyway.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.

---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
       choose an index scan if your joining column's datatypes do not
       match

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