Re NOT EXISTS SQL QUERY

Question

Hai ,
I am having doubt regarding NOT EXISTS sql query,
I want to select rows from table1 where column2 < column3 and column1 value should not exists in another two tables.
When i tried with NOT IN clause i got the answer but i didnt get when i tried with NOT EXISTS.....can anyone give me the answer....
select * from TABLE1 where mark2< mark3 AND
name NOT IN (select name from TABLE2 UNION
select name from TABLE3);

Answer 1

Your query can be re-written in the following way by using not exists clause:
SELECT     *
  FROM     table1 t1
  WHERE     mark2 < mark3
  AND     NOT EXISTS (
       SELECT     1
         FROM     table2
         WHERE     name = t1.name)
  AND     NOT EXISTS (
       SELECT     1
         FROM     table3
         WHERE     name = t1.name)Go through http://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:442029737684
on when to use NOT IN and NOT EXISTS.
Hope this is helpful.
- RK