Wierd stuff

Hi

I'm developing a system with a large number of tables.

One of the tables has (among others) the following fields:
Table = aluno
+----------------------------------+---------------------------------
| Field | Type
+----------------------------------+---------------------------------
| numero_aluno | int4
| freguesia_naturalidade | int2
| concelho_naturalidade | int2
| nacionalidade | int2

another is like this:

-- Table = concelho
+----------------------------------+---------------------------------
| Field | Type
+----------------------------------+---------------------------------
| codigo | int4
| nome | text

The field "concelho_naturalidade" on the first table has values taken
from the "codigo" field from the second.

Now comes the problem:

When i do :
sac=> select a.numero_aluno, a.concelho_naturalidade from aluno a where
a.numero_aluno=13792;

i get:

numero_aluno|concelho_naturalidade
------------+---------------------
13792| 1006
(1 row)

and whith:
sac=> select * from concelho where codigo=1006;

i get:

codigo|nome
------+----------------
1006|CALDAS DA RAINHA
(1 row)

but with:
sac=> select c.nome from aluno a, concelho c where
a.concelho_naturalidade=c.codigo and a.numero_aluno=13792;

i get:

nome
----
(0 rows)

If my SQL is worth anything I thought it would reply "Caldas da Rainha".
What is wrong here?

I'm using POstgresql 6.3.2 (yes i know: I should upgrade)

Thanks

--
Mario Filipe
mjnf(at)uevora(dot)pt
http://neptuno.sc.uevora.pt/~mjnf