Combining UNION ALL and ORDER BY in Firebird

Question

This is my first attempt at answering my own question, since someone may well run into this and so it might be of help. Using Firebird, I want to combine the results of two

Answer 1

Moving order by into a query tail has no effect to output datagrid.

select * from (
    select first 1
        C1
    from T1
    order by id desc
)
union all
select * from (
    select first 1
        C1
    from T2
    order by id desc
)