HOW TO MAKE AN UPDATE COMMAND MORE EFFICIENT

Question

hI Everyone,
if we have round (10000000) records in a table and we want to update an attribute in this table. it takes sometime round 60 mins or even more, while both tables are indexed. Do anyone knows any magic to improve the efficiency.
Best Regards,

Answer 1

If you are using IN clause, try using exists.
AdinathWhy?
look at this
1) NOT IN vs NOT EXISTS:
/*$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*/
/*$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*/
  select *
    from dept
   where deptno not in (
                         select deptno
                           from emp
                          where deptno is not null
  Statement Id=12200   Type=
  Cost=2,64022111505165E-308  TimeStamp=03-05-07::13::40:08
       (1)  SELECT STATEMENT  ALL_ROWS
     Est. Rows: 1  Cost: 6
       (6)  MERGE JOIN ANTI
     Est. Rows: 1  Cost: 6
           (3)  TABLE TABLE ACCESS BY INDEX ROWID SCOTT.DEPT  [Analyzed]
           (3)   Blocks: 5 Est. Rows: 4 of 4  Cost: 2
                Tablespace: USERS
               (2)  INDEX (UNIQUE) INDEX FULL SCAN SCOTT.PK_DEPT  [Analyzed]
                    Est. Rows: 4  Cost: 1
           (5)  SORT UNIQUE
                Est. Rows: 14  Cost: 4
               (4)  TABLE TABLE ACCESS FULL SCOTT.EMP  [Analyzed]
               (4)   Blocks: 5 Est. Rows: 14 of 14  Cost: 3
                    Tablespace: USERS
/*$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*/
/*$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*/
  select *
    from dept
   where not exists (
                      select null
                        from emp
                       where emp.deptno is not null
                         and emp.deptno = dept.deptno
  Statement Id=100   Type=
  Cost=1,95696055847079E-307  TimeStamp=03-05-07::13::42:35
       (1)  SELECT STATEMENT  ALL_ROWS
     Est. Rows: 1  Cost: 6
       (6)  MERGE JOIN ANTI
     Est. Rows: 1  Cost: 6
           (3)  TABLE TABLE ACCESS BY INDEX ROWID SCOTT.DEPT  [Analyzed]
           (3)   Blocks: 5 Est. Rows: 4 of 4  Cost: 2
                Tablespace: USERS
               (2)  INDEX (UNIQUE) INDEX FULL SCAN SCOTT.PK_DEPT  [Analyzed]
                    Est. Rows: 4  Cost: 1
           (5)  SORT UNIQUE
                Est. Rows: 14  Cost: 4
               (4)  TABLE TABLE ACCESS FULL SCOTT.EMP  [Analyzed]
               (4)   Blocks: 5 Est. Rows: 14 of 14  Cost: 3
                    Tablespace: USERS
/*$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*/
/*$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*/2) IN vs EXISTS
/*$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*/
/*$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*/
  select *
    from dept
   where exists (
                  select null
                    from emp
                   where emp.deptno is not null
                     and emp.deptno = dept.deptno
  Statement Id=100   Type=
  Cost=1,9569605606389E-307  TimeStamp=03-05-07::13::43:15
       (1)  SELECT STATEMENT  ALL_ROWS
     Est. Rows: 3  Cost: 7
       (4)  HASH JOIN SEMI
     Est. Rows: 3  Cost: 7
           (2)  TABLE TABLE ACCESS FULL SCOTT.DEPT  [Analyzed]
           (2)   Blocks: 5 Est. Rows: 4 of 4  Cost: 3
                Tablespace: USERS
           (3)  TABLE TABLE ACCESS FULL SCOTT.EMP  [Analyzed]
           (3)   Blocks: 5 Est. Rows: 14 of 14  Cost: 3
                Tablespace: USERS
/*$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*/
/*$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$*/
  select *
    from dept
   where deptno in (
                     select emp.deptno
                       from emp
                      where emp.deptno is not null
  Statement Id=4203132   Type=
  Cost=2,64022111505165E-308  TimeStamp=03-05-07::13::44:16
       (1)  SELECT STATEMENT  ALL_ROWS
     Est. Rows: 3  Cost: 7
       (4)  HASH JOIN SEMI
     Est. Rows: 3  Cost: 7
           (2)  TABLE TABLE ACCESS FULL SCOTT.DEPT  [Analyzed]
           (2)   Blocks: 5 Est. Rows: 4 of 4  Cost: 3
                Tablespace: USERS
           (3)  TABLE TABLE ACCESS FULL SCOTT.EMP  [Analyzed]
           (3)   Blocks: 5 Est. Rows: 14 of 14  Cost: 3
                Tablespace: USERS