Prob. with where clause with rownum

Question

hi
i have a table with the following columns
SQL> desc mark
Name Null? Type
STUDENTCODE NUMBER(3)
MARK1 NUMBER(2)
MARK2 NUMBER(3)
and here are the rows in it
SQL> select * from mark ;
STUDENTCODE MARK1 MARK2
1 20 40
2 70 80
3 80 90
4 90 99
12 13 35
5 90 80
6 78 87
i wanna sum mark1 and mark2 and list down the rows with the top 2 rows
i tried to first list down all the rows in the order of sum with the following stat.
SQL> select studentcode,mark1+mark2 from mark order by mark1+mark2 desc
STUDENTCODE MARK1+MARK2
4 189
3 170
5 170
6 165
2 150
1 60
12 48
it worked fine. but i used a where clause to get the first 2 rows and here is what i got.
SQL> select studentcode,mark1+mark2 from mark where rownum < 3 order by (mark1+mark2) desc
STUDENTCODE MARK1+MARK2
3 170
2 150
1 60
as You can see, i don't get the req. result.
how do i get the prob. solved ?

Answer 1

For Oracle versions prior to 8.1.5, you will have to create a view and then incorporate that view into your select statement.
create or replace view my_view
is
select studentcode, mark1 + mark2
from mark
order by mark1 + mark2 desc;
select *
from my_view
where rownum <= 2