From: | Christian Fowler <spider(at)viovio(dot)com> |
---|---|
To: | "Roderick A(dot) Anderson" <raa(at)mailporter(dot)net> |
Cc: | Jaime Casanova <systemguards(at)yahoo(dot)com>, pgsql-admin(at)postgresql(dot)org |
Subject: | Re: joins INNER, OUTER, LEFT, RIGHT, FULL, ... |
Date: | 2004-11-24 06:32:37 |
Message-ID: | Pine.LNX.4.61.0411240130250.20105@leda.steelsun.com |
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Thread: | |
Lists: | pgsql-admin |
On Tue, 23 Nov 2004, Roderick A. Anderson wrote:
> Jaime Casanova wrote:
>
>> http://www.postgresql.org/docs/7.4/static/queries-table-expressions.html#QUERIES-JOIN
>>
> Been there, done that. Bought several tee-shirts.
>
>> What do you mean with *complex joins*?
>>
>
> SELECT first, last, username || '@' || dom.domain as emailaddress
> FROM cust_main cm
> LEFT OUTER JOIN cust_pkg cp ON ( cm.custnum = cp.custnum )
> LEFT OUTER JOIN cust_svc cs ON ( cp.pkgnum = cs.pkgnum )
> LEFT OUTER JOIN svc_email em ON ( cs.svcnum = em.svcnum )
> LEFT OUTER JOIN svc_domain dom ON ( em.domain = dom.svcnum )
> WHERE zip = '99999'
> AND username || '@' || dom.domain != '@'
>
> Which worked until I added one more table with a one-to-one relation to
> cust_main.custnum. Then I got several tuples (2+) for each row above.
try:
SELECT first, last, username || '@' || dom.domain as emailaddress
FROM cust_main cm
INNER JOIN one_more om ON ( om.custnum = cm.custnum )
LEFT OUTER JOIN cust_pkg cp ON ( cm.custnum = cp.custnum )
LEFT OUTER JOIN cust_svc cs ON ( cp.pkgnum = cs.pkgnum )
LEFT OUTER JOIN svc_email em ON ( cs.svcnum = em.svcnum )
LEFT OUTER JOIN svc_domain dom ON ( em.domain = dom.svcnum )
WHERE zip = '99999'
AND username || '@' || dom.domain != '@'
or
SELECT first, last, username || '@' || dom.domain as emailaddress
FROM one_more om, cust_main cm
LEFT OUTER JOIN cust_pkg cp ON ( cm.custnum = cp.custnum )
LEFT OUTER JOIN cust_svc cs ON ( cp.pkgnum = cs.pkgnum )
LEFT OUTER JOIN svc_email em ON ( cs.svcnum = em.svcnum )
LEFT OUTER JOIN svc_domain dom ON ( em.domain = dom.svcnum )
WHERE zip = '99999'
AND om.custnum=cm.custnum
AND username || '@' || dom.domain != '@'
The explicit join syntax was freaky for me too at first, but after
several years, I prefer it now, since you can easily control your left
outer joins
[ \ /
[ >X< Christian Fowler | spider AT viovio.com
[ / \ http://www.viovio.com | http://www.tikipro.org
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