Query Question

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                      -----=====:::::~ ]

Advertising Age Global Agency of the Year 2008
Adweek Global Agency of the Year 2008

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