Swapping column values in Oracle

Question

I was solving one of the puzzles and came across swapping column values using DML queries:

SELECT * FROM TEMP_TABLE;
ID1, ID2
--------
20, 15
20, 15
20, 15
         


        

Answer 1

Before:

select * from employ;

EMPNO FNAME      LNAME
----- ---------- ----------
 1001 kiran      kumar

 1002 santosh    reddy


update employ e set fname=(select lname from employ where empno=e.empno),
                    lname=(select fname from employ where empno=e.empno);

After:

 select * from employ;

 EMPNO FNAME      LNAME
------ ---------- ----------
  1001 kumar      kiran

  1002 reddy      santosh