no_merge hint

This is tested in 10gR2.

SQL> select * from v$version;
 
BANNER
------------------------------------------------
Oracle Database 10g Enterprise Edition Release 1
0.2.0.5.0 - 64bi
 
PL/SQL Release 10.2.0.5.0 - Production
CORE    10.2.0.5.0      Production
TNS for Solaris: Version 10.2.0.5.0 - Production
NLSRTL Version 10.2.0.5.0 - Production

　　

First, we create a view.

SQL> create view v_dept as select deptno,dname from dept;
 
View created.

　　

Then check SQL

SQL> explain plan for select e.ename,d.dname from emp2 e, v_dept d where e.deptno=d.deptno;
 
Explained.
 
SQL> set linesize 180
SQL> select * from table(dbms_xplan.display());
 
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 827386235
 
----------------------------------------------------------------------------------------
| Id  | Operation                    | Name    | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT             |         |    14 |   308 |     6  (17)| 00:00:01 |
|   1 |  MERGE JOIN                  |         |    14 |   308 |     6  (17)| 00:00:01 |
|   2 |   TABLE ACCESS BY INDEX ROWID| DEPT    |     4 |    52 |     2   (0)| 00:00:01 |
|   3 |    INDEX FULL SCAN           | PK_DEPT |     4 |       |     1   (0)| 00:00:01 |
|*  4 |   SORT JOIN                  |         |    14 |   126 |     4  (25)| 00:00:01 |
|   5 |    TABLE ACCESS FULL         | EMP2    |    14 |   126 |     3   (0)| 00:00:01 |
 
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
----------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   4 - access("E"."DEPTNO"="DEPTNO")
       filter("E"."DEPTNO"="DEPTNO")
 
18 rows selected.

　　

use no_merge

SQL>  explain plan for select /*+ no_merge(d) */ e.ename,d.dname from emp2 e, v_dept d where e.deptno=d.deptno;
 
Explained.
 
SQL> select * from table(dbms_xplan.display());
 
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 2242990105
 
------------------------------------------------------------------------------
| Id  | Operation           | Name   | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |        |    14 |   434 |     7  (15)| 00:00:01 |
|*  1 |  HASH JOIN          |        |    14 |   434 |     7  (15)| 00:00:01 |
|   2 |   VIEW              | V_DEPT |     4 |    88 |     3   (0)| 00:00:01 |
|   3 |    TABLE ACCESS FULL| DEPT   |     4 |    52 |     3   (0)| 00:00:01 |
|   4 |   TABLE ACCESS FULL | EMP2   |    14 |   126 |     3   (0)| 00:00:01 |
------------------------------------------------------------------------------
 
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   1 - access("E"."DEPTNO"="D"."DEPTNO")
 
16 rows selected.
 
SQL>