Row to Column and Column to Row conversion in query

Question

I want to invert the data in my table, i.e. convert a:

1. Row to Column.
2. Column to Row.

The actual table data is

                col1     col2
---------------------------------
row1              1        2
row2              3        4

Expected output :

                col1     col2
---------------------------------
row1              1        3
row2              2        4

I have tired with a normal select query but couldn't work out how to do this. Is it possible in PL/SQL?

Answer 1

 (select * from (select a,b from t) pivot(sum(a) for b in(2,4)))

 union

 (select * from (select a,b from t) pivot(sum(b) for a in(1,3)));