Re: joins INNER, OUTER, LEFT, RIGHT, FULL, ...

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

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