ORACLE的分组统计之ROLLUP(一)

时间 2019-11-19

标签 oracle 分组统计 rollup 栏目 Oracle 繁體版

原文原文链接

Oracle 9i之后，扩展了group by 的功能，可以知足大部分多维数据的分析统计功能，主要表现：ide

1. rollup,cube,grouping sets 扩展group by字句提供了丰富的多维分组统计功能；函数

2. 3个扩展分组函数：grouping,grouping_id,group_id提供扩展group by的辅助功能:提供区别结果行属于哪一个分组级别，区分NULL值，创建有意义的报表，对汇总结果排序，过滤结果行等；性能

3.对扩展group by容许按重复列分组，组合列分组，链接分组等，另外，grouping sets能够接受cube,rollup操做做为参数。spa

ROLLUPorm

没有rollup的union all功能排序

SQL> select a.dname, b.job, sum(b.sal) sum_sal
from scott.dept a, scott.emp b
where a.deptno = b.deptno
group by a.dname, b.job
union all
select a.dname, NULL, sum(b.sa l) sum_sal
from scott.dept a, scott.emp b
where a.deptno = b.deptno
group by a.dnam e
union all
select null, null, sum(b.sal) sum_sal
from scott.dept a, scott.emp b wh ere a.deptno = b.deptno;

显示结果：索引

DNAME          JOB          SUM_SAL
-------------- --------- ----------
SALES          MANAGER         2850
SALES          CLERK            950
ACCOUNTING     MANAGER         2450
ACCOUNTING     PRESIDENT       5000
ACCOUNTING     CLERK           1300
SALES          SALESMAN        5600
RESEARCH       MANAGER         2975
RESEARCH       ANALYST         6000
RESEARCH       CLERK           1900
ACCOUNTING                     8750
RESEARCH                      10875

DNAME          JOB          SUM_SAL
-------------- --------- ----------
SALES                          9400
                              29025

已选择13行。

执行计划
----------------------------------------------------------
Plan hash value: 3113041979

--------------------------------------------------------------------------------
----------
| Id  | Operation                      | Name    | Rows  | Bytes | Cost (%CPU)|
Time     |
--------------------------------------------------------------------------------
----------
|   0 | SELECT STATEMENT               |         |    19 |   479 |    13  (70)|
00:00:01 |
|   1 |  UNION-ALL                     |         |       |       |            |
         |
|   2 |   HASH GROUP BY                |         |    14 |   392 |     5  (20)|
00:00:01 |
|   3 |    NESTED LOOPS                |         |    14 |   392 |     4   (0)|
00:00:01 |
|   4 |     TABLE ACCESS FULL          | EMP     |    14 |   210 |     3   (0)|
00:00:01 |
|   5 |     TABLE ACCESS BY INDEX ROWID| DEPT    |     1 |    13 |     1   (0)|
00:00:01 |
|*  6 |      INDEX UNIQUE SCAN         | PK_DEPT |     1 |       |     0   (0)|
00:00:01 |
|   7 |   HASH GROUP BY                |         |     4 |    80 |     5  (20)|
00:00:01 |
|   8 |    NESTED LOOPS                |         |    14 |   280 |     4   (0)|
00:00:01 |
|   9 |     TABLE ACCESS FULL          | EMP     |    14 |    98 |     3   (0)|
00:00:01 |
|  10 |     TABLE ACCESS BY INDEX ROWID| DEPT    |     1 |    13 |     1   (0)|
00:00:01 |
|* 11 |      INDEX UNIQUE SCAN         | PK_DEPT |     1 |       |     0   (0)|
00:00:01 |
|  12 |   SORT AGGREGATE               |         |     1 |     7 |            |
         |
|* 13 |    TABLE ACCESS FULL           | EMP     |    14 |    98 |     3   (0)|
00:00:01 |
--------------------------------------------------------------------------------
----------

Predicate Information (identified by operation id):
---------------------------------------------------

   6 - access("A"."DEPTNO"="B"."DEPTNO")
  11 - access("A"."DEPTNO"="B"."DEPTNO")
  13 - filter("B"."DEPTNO" IS NOT NULL)


统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
         53  consistent gets
          0  physical reads
          0  redo size
        780  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)
         13  rows processed

能够看到，须要屡次访问emp，dept表以及dept表的索引。

修改为：ip

select a.dname, b.job, sum(b.sal) sum_sal
  from scott.dept a, scott.emp b
 where a.deptno = b.deptno
 group by rollup(a.dname, b.job);

结果以下：get

DNAME          JOB          SUM_SAL
-------------- --------- ----------
SALES          CLERK            950
SALES          MANAGER         2850
SALES          SALESMAN        5600
SALES                          9400
RESEARCH       CLERK           1900
RESEARCH       ANALYST         6000
RESEARCH       MANAGER         2975
RESEARCH                      10875
ACCOUNTING     CLERK           1300
ACCOUNTING     MANAGER         2450
ACCOUNTING     PRESIDENT       5000

DNAME          JOB          SUM_SAL
-------------- --------- ----------
ACCOUNTING                     8750
                              29025


  
  
  
  
   
   
   
   执行计划
----------------------------------------------------------
Plan hash value: 503922295

--------------------------------------------------------------------------------
---------
| Id  | Operation                     | Name    | Rows  | Bytes | Cost (%CPU)| T
ime     |
--------------------------------------------------------------------------------
---------
|   0 | SELECT STATEMENT              |         |    14 |   392 |     5  (20)| 0
0:00:01 |
|   1 |  SORT GROUP BY ROLLUP         |         |    14 |   392 |     5  (20)| 0
0:00:01 |
|   2 |   NESTED LOOPS                |         |    14 |   392 |     4   (0)| 0
0:00:01 |
|   3 |    TABLE ACCESS FULL          | EMP     |    14 |   210 |     3   (0)| 0
0:00:01 |
|   4 |    TABLE ACCESS BY INDEX ROWID| DEPT    |     1 |    13 |     1   (0)| 0
0:00:01 |
|*  5 |     INDEX UNIQUE SCAN         | PK_DEPT |     1 |       |     0   (0)| 0
0:00:01 |
--------------------------------------------------------------------------------
---------

Predicate Information (identified by operation id):
---------------------------------------------------

   5 - access("A"."DEPTNO"="B"."DEPTNO")


统计信息
----------------------------------------------------------
          1  recursive calls
          0  db block gets
         23  consistent gets
          0  physical reads
          0  redo size
        750  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)
         13  rows processed
  
  
  
  

已选择13行。

可见，使用rollup只须要访问emp表一次，经过dept表的主键得到rowid表查询相关行，比union all性能要好。 hash