I'm using firebird 1.0.

When I try to do

select book_id, price, '' as condition from Book
UNION
select bk.book_id, price, condition from Stock sk, Book bk where
bk.book_id = sk.book_id

I keep getting

SQL error code = -104
Invalid command
Data type unknown


This works with many other databases that I have tried.

Does UNION not work with Firebird.

Thanks for the help.

Cheers
-raj