Will indexes be used on the both sides of the join?

Question

SELECT * FROM emp a, dept b WHERE a.dept_no = b.dept_no
Assume we have bitmap index on emp (dept_no) and we have binary index on dept (dept_no), will both the indexes be used for searching when equated?

Answer 1

Prasath N wrote:
I had looked the Explain plan, but it is taking only one index (index on dept (deptno)).
I tried giving hint for the other index, still no change in explain plan.
Will the other index be used while joining and not shown in explain plan?Care to show us your test case?
And your Oracle version?
Here's mine....
create table my_emp as
select *
from scott.emp
create table my_dept as
select *
from scott.dept
create index my_dept_i01 on my_dept(deptno);
create bitmap index my_emp_i01 on my_emp(deptno);
explain plan for
SELECT b.deptno
FROM my_emp a, my_dept b
  4  WHERE a.deptno = b.deptno;
Explained.
Elapsed: 00:00:00.01
TUBBY_TUBBZ?
TUBBY_TUBBZ?select * from table(dbms_xplan.display(NULL, NULL, 'ALL'));
PLAN_TABLE_OUTPUT
Plan hash value: 697535001
| Id  | Operation                     | Name        | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT              |             |    14 |   364 |     1   (0)| 00:00:01 |
|   1 |  NESTED LOOPS                 |             |    14 |   364 |     1   (0)| 00:00:01 |
|   2 |   BITMAP CONVERSION TO ROWIDS |             |    14 |   182 |     1   (0)| 00:00:01 |
|   3 |    BITMAP INDEX FAST FULL SCAN| MY_EMP_I01  |       |       |            |          |
|*  4 |   INDEX RANGE SCAN            | MY_DEPT_I01 |     1 |    13 |     0   (0)| 00:00:01 |
Query Block Name / Object Alias (identified by operation id):
   1 - SEL$1
   2 - SEL$1 / A@SEL$1
   4 - SEL$1 / B@SEL$1
Predicate Information (identified by operation id):
   4 - access("A"."DEPTNO"="B"."DEPTNO")
Column Projection Information (identified by operation id):
   1 - (#keys=0) "B"."DEPTNO"[NUMBER,22]
   2 - "A".ROWID[ROWID,10], "A"."DEPTNO"[NUMBER,22]
   3 - STRDEF[BM VAR, 10], STRDEF[BM VAR, 10], STRDEF[BM VAR, 7920],
       "A"."DEPTNO"[NUMBER,22]
   4 - "B"."DEPTNO"[NUMBER,22]
Note
   - dynamic sampling used for this statement (level=2)
36 rows selected.
Elapsed: 00:00:00.02
TUBBY_TUBBZ?
TUBBY_TUBBZ?select * from v$version;
BANNER
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE     11.2.0.1.0     Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production
5 rows selected.
Elapsed: 00:00:00.01Edited by: Tubby on May 28, 2010 9:20 AM
Added test case.