oracle 高级分组 ROLLUP

用SCOTT/TIGER登录。

ROLLUP，是GROUP BY子句的一种扩展，可以为每个分组返回小计记录以及为所有分组返回总计记录。

表EMP所有数据：

SELECT * FROM EMP;

结果：

不用ROLLUP：

SELECT JOB, SUM(SAL) FROM EMP GROUP BY JOB;

结果：

执行计划：

SQL> SELECT JOB, SUM(SAL) FROM EMP GROUP BY JOB;

JOB         SUM(SAL)
--------- ----------
CLERK           4150
SALESMAN        5600
PRESIDENT       5000
MANAGER         8275
ANALYST         6000


执行计划
----------------------------------------------------------
Plan hash value: 4067220884

---------------------------------------------------------------------------
| Id  | Operation          | Name | Rows  | Bytes | Cost (%CPU)| Time     |
---------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |      |     5 |    60 |     4  (25)| 00:00:01 |
|   1 |  HASH GROUP BY     |      |     5 |    60 |     4  (25)| 00:00:01 |
|   2 |   TABLE ACCESS FULL| EMP  |    14 |   168 |     3   (0)| 00:00:01 |
---------------------------------------------------------------------------


统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          7  consistent gets
          0  physical reads
          0  redo size
        567  bytes sent via SQL*Net to client
        385  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          5  rows processed

使用ROLLUP：

SELECT JOB, SUM(SAL) FROM EMP GROUP BY ROLLUP(JOB);

结果：

执行计划：

SQL> SELECT JOB, SUM(SAL) FROM EMP GROUP BY ROLLUP(JOB);

JOB         SUM(SAL)
--------- ----------
ANALYST         6000
CLERK           4150
MANAGER         8275
PRESIDENT       5000
SALESMAN        5600
               29025

已选择6行。


执行计划
----------------------------------------------------------
Plan hash value: 52302870

-----------------------------------------------------------------------------
| Id  | Operation            | Name | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------
|   0 | SELECT STATEMENT     |      |     5 |    60 |     4  (25)| 00:00:01 |
|   1 |  SORT GROUP BY ROLLUP|      |     5 |    60 |     4  (25)| 00:00:01 |
|   2 |   TABLE ACCESS FULL  | EMP  |    14 |   168 |     3   (0)| 00:00:01 |
-----------------------------------------------------------------------------


统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          7  consistent gets
          0  physical reads
          0  redo size
        578  bytes sent via SQL*Net to client
        385  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          1  sorts (memory)
          0  sorts (disk)
          6  rows processed