Tamas,

> I can't prepare the following sql statement on employee.fdb:
>
> update EMPLOYEE set LAST_NAME='XX'
> where ((LAST_NAME=:old_last_name1) or
> ((:old_last_name2 is null) and (LAST_NAME is null)))
>
>
> I get -804 Sql error code and Data type unknown message. I tried
> FIBPlus and IBX, both failed.
> I found that the problematic part is "(:old_last_name2 is null)"
> expression.
> If I remove that there's no trouble. What can I do?

Remove it. :-)
You can not use a field name as parameter.

Artur Anjos