Re: Problem with joining two tables

On 5 déc. 07, at 14:42, Przemyslaw Bojczuk wrote:

> Hello!
>
> I have a problem joining two tables. I tried various types of join and
> none seems to work as I expect
>
> Table 1:
>
> id | stuff
> -----------
> 1 | sth1
> 2 | sth2
> 3 | sth3
> 4 | sth4
> 5 | sth5
> .. | ...
>
> Table 2:
>
> id | desc | etc
> ------------------
> 1 | desc1 | etc1
> 2 | desc2 | etc2
> 2 | desc3 | etc3
> 2 | desc4 | etc4
> 3 | desc5 | etc5
> | desc6 | etc6
> 5 | desc7 | etc7
> .. | ... | ...
>
> I need something like:
>
> id | stuff | desc | etc
> -------------------------
> 1 | sth1 | desc1 | etc1
> 2 | sth2 | desc2 | etc2
> 2 | sth2 | desc3 | etc3
> 2 | sth2 | desc4 | etc4
> 3 | sth3 | desc5 | etc5
> 5 | sth5 | desc7 | etc7
>
> So: join by id, discard rows that don't match any row from the other
> table, add separate row for each row from table 2 that matches the
> same
> row from table 1.
>
> So far the best I could get (using inner join) was something like:
>
> id | stuff | desc | etc
> -------------------------
> 1 | sth1 | desc1 | etc1
> 2 | sth2 | desc2 | etc2
> 2 | sth2 | desc2 | etc2
> 2 | sth2 | desc2 | etc2
> 3 | sth3 | desc5 | etc5
> 5 | sth5 | desc7 | etc7
>
> (i.e. multiplied one row from table 2 instead of separate rows
> matching
> the same row from table 1)
>
> right/left/full (outer) also seem to do the same thing (multiply one
> row) and I don't know any other join methods.
>
> Is there a way to accomplish what I am trying to do? Or maybe I am
> missing something?
>
> Thanks in advance!
> PB
> --
> Geographical Information Systems Laboratory
> Institute of Earth Sciences, UMCS
> http://gis.umcs.lublin.pl/en/
>
> ---------------------------(end of
> broadcast)---------------------------
> TIP 6: explain analyze is your friend

CREATE TABLE test1(id int, stuff text);

CREATE TABLE test2(id int, descr text, etc text);

INSERT INTO test1(id, stuff) VALUES (1, 'sth1');
INSERT INTO test1(id, stuff) VALUES (2, 'sth2');
INSERT INTO test1(id, stuff) VALUES (3, 'sth3');
INSERT INTO test1(id, stuff) VALUES (4, 'sth4');
INSERT INTO test1(id, stuff) VALUES (5, 'sth5');

INSERT INTO test2(id, descr, etc) VALUES (1, 'desc1', 'etc1');
INSERT INTO test2(id, descr, etc) VALUES (2, 'desc2', 'etc2');
INSERT INTO test2(id, descr, etc) VALUES (2, 'desc3', 'etc3');
INSERT INTO test2(id, descr, etc) VALUES (2, 'desc4', 'etc4');
INSERT INTO test2(id, descr, etc) VALUES (3, 'desc5', 'etc5');
INSERT INTO test2(id, descr, etc) VALUES (null, 'desc6', 'etc6');
INSERT INTO test2(id, descr, etc) VALUES (5, 'desc7', 'etc7');

SELECT t1.id, t1.stuff, t2.descr, t2.etc
FROM test1 t1
INNER JOIN test2 t2 ON t1.id = t2.id;

id | stuff | descr | etc
----+-------+-------+------
1 | sth1 | desc1 | etc1
2 | sth2 | desc2 | etc2
2 | sth2 | desc3 | etc3
2 | sth2 | desc4 | etc4
3 | sth3 | desc5 | etc5
5 | sth5 | desc7 | etc7

seems OK for me

hope this help.
Tom