wrong query result

Hi

I just want to let you know one thing.
By the way, I'm running Postgres 8.3.1 on windows

I was making a query using pgadmin:

select clau, lecact-lecant as m3, m3any, ta, tc, 3 as mesos, persones, true
as clavegueram
from fac_abonats
where clau in (select clau from tmp_claus_prova)
order by clau

clau is the primary key of the table fac_abonats

the thing is that the result of the query returns the same number of rows as
the table fac_abonats (thousands).
select clau from tmp_claus_prova return about one hundred rows, and all the
values in the column exists
in fac_abonats. So maybe something wrong is happening in the where clause.

At the end I've realized that there is no column named 'clau'. It has
another name.
So the subselect query is wrong, if I execute it alone, an error appears

ERROR: no existe la columna «clau»
LINE 6: select clau from tmp_claus_prova
^

********** Error **********

ERROR: no existe la columna «clau»
Estado SQL:42703
Caracter: 188

The question is:
Is it a normal behaviour? Because I think that if the query is wrong,
wouldn't be better to raise an error?

Regards,

Josep Porres