Help with order by

Question

I want to select the same column name from 2 tables, combine them, and give them a certain order but I am getting:
ORA-01785: ORDER BY item must be the number of a SELECT-list expression
select a from table1 where a = 'TYY000007'
union all
select a from table2 where a = 'TXXXXXXXX'
order by TRANSLATE(a, 'ABCDEFGHIJKMNOPQRSUVWXYTL0123456789','0123456789ABCDEFGHIJKMNOPQRSUVWXYTL') DESC;
I know the TRANSLATE works because it will work with just 1 table query and I've used it in other queries.
Please help.

Answer 1

Hi,
Noramally, you can ORDER BY something that is not in the SELECT clause.
In a UNION query, you can't.
if you want to ORDER BY d046d (or something derived from it), then you have to include d046d in the SELECT clause. To avoid displaying it, you can do the UNION in a sub-query, like this:
WITH     union_results     AS
     select a, d046d from table1 where a = 'TYY000007'     -- This is easy to do without a UNION,
     union all                                              -- but that's not the point
     select a, d046d from table2 where a = 'TXXXXXXXX'
SELECT       a
FROM       union_results
ORDER BY  TRANSLATE ( d046d
                      , 'ABCDEFGHIJKMNOPQRSUVWXYTL0123456789'
              , '0123456789ABCDEFGHIJKMNOPQRSUVWXYTL'
              )          DESC
;