Try working with this:
SELECT m.key AS mailings_key,
m.name AS mailings_name,
COALESCE(u.key,'') AS userdata_key,
COALESCE(u.uid,'') AS userdata_uid,
COALESCE(u.name,'') AS userdata_name
FROM (SELECT m0.key, m0.name, u0.uid
FROM mailings m0, (SELECT DISTINCT uid FROM userdata) AS u0
ORDER BY u0.uid, m0.key) AS m
LEFT OUTER JOIN userdata u ON u.key = m.key AND u.uid = m.uid
ORDER BY m.uid, m.key
Cheers,
Ioana
--- On Tue, 2/10/09, Schwaighofer Clemens <clemens.schwaighofer@xxxxxxxxxx> wrote:
> From: Schwaighofer Clemens <clemens.schwaighofer@xxxxxxxxxx>
> Subject: Query Question
> To: pgsql-general@xxxxxxxxxxxxxx
> Received: Tuesday, February 10, 2009, 5:30 AM
> I have two tables
>
> Table "public.mailings"
> Column | Type | Modifiers
> --------+-------------------+-----------
> key | character varying |
> name | character varying |
>
> Table "public.userdata"
> Column | Type | Modifiers
> --------+-------------------+-----------
> key | character varying |
> uid | character varying |
> name | character varying |
>
> which hold the following data
>
> mailing:
>
> key | name
> -----+--------
> A1 | Test 1
> A2 | Test 2
> A3 | Test 3
> A4 | Test 4
>
> userdata:
>
> key | uid | name
> -----+-----+--------
> A1 | B1 | Test 1
> A3 | B1 | Test 3
> A2 | B2 | Test 2
> A3 | B2 | Test 3
> A4 | B2 | Test 4
> A2 | B2 | Test 2
> A1 | B3 | Test 1
> A4 | B3 | Test 4
> A1 | B4 | Test 1
> A2 | B5 | Test 2
> A3 | B5 | Test 3
> A4 | B5 | Test 4
> A1 | B6 | Test 1
> A2 | B6 | Test 2
> A3 | B6 | Test 3
> A4 | B6 | Test 4
>
> I want to select the data between userdata and mailings,
> that adds me
> a null row to the mailings if mailing table does not have a
> matching
> row for "key" in the grouping "uid".
>
> So eg the result should look like this
>
> key | name | key | uid | name
> -----+--------+-----+-----+--------
> A1 | Test 1 | A1 | B1 | Test 1
> A2 | Test 2 | | |
> A3 | Test 3 | A3 | B1 | Test 3
> A4 | Test 4 | | |
> A1 | Test 1 | | |
> A2 | Test 2 | A2 | B2 | Test 2
> A2 | Test 2 | A2 | B2 | Test 2
> A3 | Test 3 | A3 | B2 | Test 3
> A4 | Test 4 | A4 | B2 | Test 4
> ...
>
> but my problem is, that a normal join will not work,
> because both
> tables will hold a complete set of matching "key"
> data. I need to sub
> group the join through the "uid" column from the
> userdata.
>
> But i have no idea how to do this. Any idea if there is a
> simple way to do this?
>
> --
> [ Clemens Schwaighofer
> -----=====:::::~ ]
>
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