See the following SQL below. If I select from COMBINED, the sql runs but as below I get an error. This is pretty annoying when constructing a large SQL with many CTEs and you want to test each one and combinations of them. I can get why the error is there, but any other suggestion?
with
CTE1 as
(
select 1 as ID from rdb$database
),
CTE2 as
(
select 2 as ID from rdb$database
),
COMBINED as
(
select * from CTE1
union
select * from CTE2
)
select * from CTE1
