How can I calculate the max value of two columns with a single query.
Suppose I have a table with the following information:

id col1 col2
-- ---- ----
1 10 20
2 20 30
3 12 23

The query should return the following data:

id max_value
-- ----------
1 20
2 30
3 23

Thanks in advance,
Carlos Dias

Hi Carlos,

How about the following ?

--------------------------------------------
SQL> select * from t;

        ID COL1 COL2
---------- ---------- ----------
         1 10 20
         2 20 30
         3 12 23

SQL> select id, max(col) from (
  2 select id, col1 as col from t
  3 union
  4 select id, col2 as col from t
  5 )
  6 group by id;

        ID MAX(COL)
---------- ----------
         1 20
         2 30
         3 23

SQL>
--------------------------------------------

Cheers,
Prat