number to string conversion

Hi everybody,

I wanted to do something like the following:

SELECT

p.*, (SELECT c.* FROM CCAA c WHERE c.ccaa_id_ccaa = p.prov_id_ccaa)

FROM

PROVINCIA p

WHERE

(prov_id_ccaa = '@@@id_ccaa@@@' OR '' = '@@@id_ccaa@@@') AND

(upper(prov_ds_provincia) LIKE upper('%@@@descripcion@@@%') OR
'@@@descripcion@@@' = '')

...where anything between "@@@" is a token that is replaced by some
value at runtime.

There is a particular case: null values. In those cases, you'd get a
query like this:

SELECT

p.*, (SELECT c.* FROM CCAA c WHERE c.ccaa_id_ccaa = p.prov_id_ccaa)

FROM

PROVINCIA p

WHERE

(prov_id_ccaa = '' OR '' = '') AND

(upper(prov_ds_provincia) LIKE upper('xxx') OR 'xxx' = '')

Being prov_id_ccaa a numeric column, in ORACLE and Access, this wouldn't
pose a problem, but it PostgreSQL it does (it throws the error: ERROR:
invalid input syntax for type numeric: ")

The only solution I can think of is converting prov_id_ccaa to a string
value (something like to_char in ORACLE, for instance)

How can I do that (in PostgreSQL)?

Can anybody else think of a better solution?

Regards,

Freddy.