HELP: SELECT MAX( Exp1, Exp2)

Question

SELECT MAX( 1,2,3) FROM DUAL:
Should return 3 but it does not. Each element 1 2 3 is an expression. According to "Oracle 9i SQL Ref" MAX uses standard sql Expressions which Includes an Expression List which is delimited by "," Since SELECT MAX(2) FROM DUAL Returns 2 it should iterate.
I have a table
ID: VAL1: VAL2
I want to query and return 2 columns
ID: MAX(VAL1,VAL2)
I know I probably forgot something stupid.
Thank you for any help.

Answer 1

max finds the maximum value from one column (or expression) from multiple rows.
so this will work:
select max(x) from (
select 1 x from dual
union
select 2 from dual
union
select 3 from dual
to find the maximum value from different columns from one row use "greatest".
select greatest(1,2,3) from dual;