Re: Join Advice and Assistance

[Stephen Belcher <sycobuny(at)malkier(dot)net>]

To expand on Rob's reply:

If you want to return a single row for each user, regardless of the number
of email addresses, you might use ARRAY() with a subquery, eg (haven't
tested this to make sure it completely works):

SELECT u.*, um.*, ARRAY(SELECT emailaddr FROM user_emailaddrs em WHERE
em.userid = u.userid AND em.is_active) AS email_addresses
FROM users u INNER JOIN usermetas um ON u.userid = um.userid;

Of course, this will return the addresses as a character varying[], with
output like {user(at)domain(dot)tld,user(at)domain(dot)tld}, and would require some minor
contortions to present it to users cleanly. The array_to_string function may
help you make it easier to display the results.

http://www.postgresql.org/docs/8.4/static/functions-array.html#ARRAY-FUNCTIONS-TABLE

Hope this helps,
--Stephen Belcher

On Mon, Feb 22, 2010 at 12:05 PM, Rob Sargent <robjsargent(at)gmail(dot)com> wrote:

> My mistake.  Should answer these things late at night.
>
> I think you will find that arrays will be your friend[s]
>
>
> On 02/22/2010 08:51 AM, Gary Chambers wrote:
>
>> Rob,
>>
>> Thanks for the reply...
>>
>>  If you want records for user without email addresses you will need an
>>> outer
>>> join on user_emailaddrs
>>>
>>> /* untested */
>>> select u.userId, u.lname, u.lastname ,m.startdate, a.emailaddr
>>> from users u
>>> join usermetas m on u.userid = m.userid
>>> left join user_emailaddrs a on m.userid = a.userid
>>>
>>
>> My question was related more toward eliminating the query returning a
>> record for each record in the one-to-many table.  I see now that I'm
>> going to have to aggregate the e-mail addresses in order to return a
>> single row.  Thanks again.
>>
>> -- Gary Chambers
>>
>> /* Nothing fancy and nothing Microsoft! */
>>
>
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