select e.last_name, e.department_id, d.department_name
from hr.employees e
left outer join hr.departments d on (e.department_id = d.department_id);
select e.last_name, e.department_id, d.department_name
from hr.employees e
left outer join hr.departments d on ( d.department_id=e.department_id );
SQL> select e.last_name, e.department_id, d.department_name
from hr.employees e
left outer join hr.departments d on (e.department_id = d.department_id); 2 3
107 rows selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 2296652067
----------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 107 | 2889 | 7 (15)| 00:00:01 |
|* 1 | HASH JOIN OUTER | | 107 | 2889 | 7 (15)| 00:00:01 |
| 2 | TABLE ACCESS FULL| EMPLOYEES | 107 | 1177 | 3 (0)| 00:00:01 |
| 3 | TABLE ACCESS FULL| DEPARTMENTS | 27 | 432 | 3 (0)| 00:00:01 |
----------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("E"."DEPARTMENT_ID"="D"."DEPARTMENT_ID"(+))
SQL> select e.last_name, e.department_id, d.department_name
from hr.employees e
left outer join hr.departments d on ( d.department_id=e.department_id ); 2 3
107 rows selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 2296652067
----------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 107 | 2889 | 7 (15)| 00:00:01 |
|* 1 | HASH JOIN OUTER | | 107 | 2889 | 7 (15)| 00:00:01 |
| 2 | TABLE ACCESS FULL| EMPLOYEES | 107 | 1177 | 3 (0)| 00:00:01 |
| 3 | TABLE ACCESS FULL| DEPARTMENTS | 27 | 432 | 3 (0)| 00:00:01 |
----------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("D"."DEPARTMENT_ID"(+)="E"."DEPARTMENT_ID")
(e.department_id = d.department_id)和( d.department_id=e.department_id )位置没有影响。