Re: SELECT from multiple tables (not join though)

Am Montag, 10. Januar 2005 18:22 schrieb Madison Kelly:
> Hi all,
>
> I have another question, I hope it isn't too basic. ^.^
>
> I want to do a select from multiple tables but not join them. What I
> am trying to do is something like this (though this doesn't work as I
> need):
>
> SELECT a.file_name, b.file_name, c.file_name FROM file_info_1 a,
> file_info_2 b, file_info_3 c WHERE a.file_name='/' AND
> b.file_parent_dir='/' AND c.file_parent_dir='/';
>
> That returns every combination of the results from the three tables
> which is a huge number. What I need is to return all of the matches in
> all of the tables in a single column. Once I have all the matches in one
> column the next trick is to sort the combined results (any tips there?).

you want something like this

SELECT a.file_name
FROM file_info_1 a
WHERE a.file_name='/'

UNION

SELECT b.file_name
FROM file_info_2 b
WHERE b.file_name='/'

UNION

SELECT c.file_name
FROM file_info_3 c
WHERE c.file_name='/'

ORDER BY 1;

for further documentation visit

http://www.postgresql.org/docs/7.4/interactive/sql-select.html

or your local postgresql documentation.

kind regards,
janning