dbms:oracle:devel:group
문서의 이전 판입니다!
그냥 참조용.
SQL> select department_id from employees;
DEPARTMENT_ID
90
90
90
60
60
60
50
50
50
50
50
80
80
80
10
20
20
110
110
20 rows selected.
Execution Plan
Plan hash value: 1445457117
| Id | Operation | Name | Rows | Bytes | Cost (%CPU) | Time |
——————————————————————————-
| 0 | SELECT STATEMENT | 20 | 60 | 3 (0) | 00:00:01 | |
| 1 | TABLE ACCESS FULL | EMPLOYEES | 20 | 60 | 3 (0) | 00:00:01 |
——————————————————————————-
SQL> ed Wrote file afiedt.buf
1 select department_id from employees 2* group by department_id
SQL> /
DEPARTMENT_ID
90
20
110
50
80
60
10
8 rows selected.
Execution Plan
Plan hash value: 1192169904
| Id | Operation | Name | Rows | Bytes | Cost (%CPU) | Time |
——————————————————————————–
| 0 | SELECT STATEMENT | 7 | 21 | 4 (25) | 00:00:01 | |
| 1 | HASH GROUP BY | 7 | 21 | 4 (25) | 00:00:01 | |
| 2 | TABLE ACCESS FULL | EMPLOYEES | 20 | 60 | 3 (0) | 00:00:01 |
——————————————————————————–
SQL> select distinct department_id from employees;
DEPARTMENT_ID
90
20
110
50
80
60
10
8 rows selected.
Execution Plan
Plan hash value: 3042654289
| Id | Operation | Name | Rows | Bytes | Cost (%CPU) | Time |
——————————————————————————–
| 0 | SELECT STATEMENT | 7 | 21 | 4 (25) | 00:00:01 | |
| 1 | HASH UNIQUE | 7 | 21 | 4 (25) | 00:00:01 | |
| 2 | TABLE ACCESS FULL | EMPLOYEES | 20 | 60 | 3 (0) | 00:00:01 |
——————————————————————————–
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