Hint problem

Question

Hi Experts,
I have passed full table scan hint in the below query
even I have used full table scan hint the optimizer is doing index range scan.
Why it's happening like that.
Please help me.
SQL> SELECT * FROM EMP
    WHERE deptno IN
    (SELECT /*+ FULL(emp) */ DEPTNO FROM DEPT
    WHERE DEPTNO=20);
   EMPNO ENAME                       SAL     DEPTNO       COMM
      7876 ADAMS                  13000000         20
      7369 SMITH                8.0000E+12         20
      7902 FORD                   30000000         20
      7788 SCOTT                  30000000         20
      7566 JONES                  20000000         20
Execution Plan
Plan hash value: 3939047513
| Id  | Operation          | Name          | Rows  | Bytes | Cost  |
|   0 | SELECT STATEMENT   |               |     2 |    40 |     4 |
|*  1 |  HASH JOIN SEMI    |               |     2 |    40 |     4 |
|*  2 |   TABLE ACCESS FULL| EMP           |     5 |    85 |     2 |
|*  3 |   INDEX RANGE SCAN | DEP_DEPNO_IND |     1 |     3 |     1 |
Predicate Information (identified by operation id):
   1 - access("DEPTNO"="DEPTNO")
   2 - filter("DEPTNO"=20)
   3 - access("DEPTNO"=20)
Note
   - cpu costing is off (consider enabling it)

Answer 1

user9077483 wrote:
Hi Experts,
I have passed full table scan hint in the below query
even I have used full table scan hint the optimizer is doing index range scan.
Why it's happening like that.
Please help me.
SQL> SELECT * FROM EMP
WHERE deptno IN
(SELECT /*+ FULL(emp) */ DEPTNO FROM DEPT
WHERE DEPTNO=20);
   EMPNO ENAME                       SAL     DEPTNO       COMM
7876 ADAMS                  13000000         20
7369 SMITH                8.0000E+12         20
7902 FORD                   30000000         20
7788 SCOTT                  30000000         20
7566 JONES                  20000000         20
Execution Plan
Plan hash value: 3939047513
| Id  | Operation          | Name          | Rows  | Bytes | Cost  |
|   0 | SELECT STATEMENT   |               |     2 |    40 |     4 |
|*  1 |  HASH JOIN SEMI    |               |     2 |    40 |     4 |
|*  2 |   TABLE ACCESS FULL| EMP           |     5 |    85 |     2 |
|*  3 |   INDEX RANGE SCAN | DEP_DEPNO_IND |     1 |     3 |     1 |
Predicate Information (identified by operation id):
1 - access("DEPTNO"="DEPTNO")
2 - filter("DEPTNO"=20)
3 - access("DEPTNO"=20)
Note
- cpu costing is off (consider enabling it)
I think you're very confused. Look closely at which tables are being full table scanned and which are
index range scanned, then look at your hint and what table you're hinting there.