Search Postgresql Archives

Re: Question about joins, left outer and others

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Tom Lane wrote:
Jeff Ross <jross@xxxxxxxxxx> writes:
To get the output I want above, I'd think I'd need to do a left outer join like this:

jross@wykids localhost# select ed_cat_name as "Level", pp_ed_cat_subject as "Subject", pp_ed_cat_institution as "Institution" from
education_categories left outer join people_education_categories on
(ed_cat_id = pp_ed_cat_id) where pp_ed_cat_pp_id = 1796;

This query is actually equivalent to a plain join.  The reason is that
no null-extended row can possibly satisfy the WHERE clause, since the
WHERE is constraining a field from the inner side of the join.  Remember
WHERE filters the output of the join.

Possibly what you want is

	select ... from
	education_categories left outer join people_education_categories on
	(ed_cat_id = pp_ed_cat_id and pp_ed_cat_pp_id = 1796);

			regards, tom lane


Thanks, Tom and Andy.  This is exactly what I was missing.

Jeff Ross

--
Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-general

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]
  Powered by Linux