Delete the duplicate and keep the max records.....

Question

I would like to remove the duplicate records based on columns ID and VAL but keep the max SAL records. ID + VAL is the key in the table and just delete same records by keeping the max sal.
Note: Eventhough there are two records for the same max SAL, just keep one
eg
SQL>  select * from temp_fa;
        ID        VAL        SAL
         1        100         10
         1        100         20
         1        100         20
         2        200         10
         3        300         10
         3        300         30
         4        400         10
         4        400         10
         5        500         10
         5        500         20
         5        500         20
After deleting the table should looks like
SQL>  select * from temp_fa;
        ID        VAL        SAL
         1        100         20
         2        200         10
         3        300         30
         4        400         10
         5        500         20

Answer 1

user520824 wrote:
I would like to remove the duplicate records based on columns ID and VAL but keep the max SAL records. ID + VAL is the key in the table and just delete same records by keeping the max sal.
Note: Eventhough there are two records for the same max SAL, just keep one
eg
SQL>  select * from temp_fa;
ID        VAL        SAL
1        100         10
1        100         20
1        100         20
2        200         10
3        300         10
3        300         30
4        400         10
4        400         10
5        500         10
5        500         20
5        500         20
After deleting the table should looks like
SQL>  select * from temp_fa;
ID        VAL        SAL
1        100         20
2        200         10
3        300         30
4        400         10
5        500         20
Hi,
In this script I included sal in the key because it's more safe for you.
        ID        VAL        SAL
         1        100         10
         1        100         20
         1        100         20
         2        200         10
         3        300         10
         3        300         30
         4        400         10
         4        400         10
         5        500         10
         5        500         20
         5        500         20
--1.Preserve first row from all duplicates
create table first_duplicate as
(select distinct val, id, sal
from temp_fa
where to_char(temp_fa.id)||to_char(temp_fa.val)||to_char(temp_fa.sal) in
(select to_char(temp_fa.id)||to_char(temp_fa.val)||to_char(temp_fa.sal) p_key
      from temp_fa
      group by to_char(temp_fa.id)||to_char(temp_fa.val)||to_char(temp_fa.sal)
         having count(to_char(temp_fa.id)||to_char(temp_fa.val)||to_char(temp_fa.sal))>1)
--2.Delete all duplicates
DELETE  FROM temp_fa
where to_char(temp_fa.id)||to_char(temp_fa.val)||to_char(temp_fa.sal) in 
     (select to_char(temp_fa.id)||to_char(temp_fa.val)||to_char(temp_fa.sal) p_key
     from temp_fa
     where to_char(temp_fa.id)||to_char(temp_fa.val)||to_char(temp_fa.sal) in
          (select to_char(temp_fa.id)||to_char(temp_fa.val)||to_char(temp_fa.sal) p_key
          from temp_fa
           group by to_char(temp_fa.id)||to_char(temp_fa.val)||to_char(temp_fa.sal)
              having count(to_char(temp_fa.id)||to_char(temp_fa.val)||to_char(temp_fa.sal))>1)
--3.Add first row from all duplicates
insert into  temp_fa (val, id, sal)
select * from first_duplicate;
--4.Delete rows that don't have the max salary
DELETE  FROM temp_fa
where to_char(temp_fa.id)||to_char(temp_fa.val)||to_char(temp_fa.sal) in 
     (select to_char(id)||to_char(val)||to_char(sal) p_key
     from temp_fa
          MINUS
     (select to_char(x.id)||to_char(x.val)||to_char(x.sal) p_key
     from temp_fa x,
     (select val, id, max(sal) max_val from temp_fa
       group by  val, id ) y
       WHERE x.val = y.val and
        x.id  = y.id and
        x.sal =max_val
HR: XE > select * from temp_fa order by id;
        ID        VAL        SAL
         1        100         20
         2        200         10
         3        300         30
         4        400         10
         5        500         20
HR: XE > Regards,
Ion
Edited by: user111444777 on Sep 25, 2009 10:42 PM