oracle 集合运算符

UNION/UNION ALL 并集

INTERSECT 交集

MINUS 差集

我们知道group by 增强中 http://www.cnblogs.com/liuwt365/p/4181256.html

group by rollup(a,b)
 =
 group by a,b
 +
 group by a
 +
 group by null

所以我们应该写sql语句应该为：

 1 SQL> select deptno,job,sum(sal) from emp group by deptno,job
 2   2  union
 3   3  select deptno,sum(sal) from emp group by deptno
 4   4  union
 5   5  select sum(sal) from emp group by null;
 6
 7 select deptno,job,sum(sal) from emp group by deptno,job
 8 union
 9 select deptno,sum(sal) from emp group by deptno
10 union
11 select sum(sal) from emp group by null
12
13 ORA-01789: 查询块具有不正确的结果列数

但是出错了，这是集合运算符的限制

　　1. 参与运算的各个集合必须列数相同 且类型一致
　　2. 采用第一个集合的表头作为最后的表头
　　3. 如果排序，必须在每个集合后使用相同的order by
　　4. 可以使用括号

 1 SQL> select deptno,job,sum(sal)
 2   2  from emp
 3   3  group by rollup(deptno,job)
 4   4  ;
 5
 6 DEPTNO JOB       SUM(DEPTNO)
 7 ------ --------- -----------
 8     10 CLERK              10
 9     10 MANAGER            10
10     10 PRESIDENT          10
11     10                    30
12     20 CLERK              20
13     20 ANALYST            20
14     20 MANAGER            20
15     20                    60
16     30 CLERK              30
17     30 MANAGER            30
18     30 SALESMAN          120
19     30                   180
20                          270
21
22 13 rows selected
23
24 SQL> select deptno,job,sum(sal) from emp group by deptno,job
25   2  union
26   3  select deptno,to_char(null),sum(sal) from emp group by deptno
27   4  union
28   5  select to_number(null),to_char(null),sum(sal) from emp group by null;
29
30     DEPTNO JOB         SUM(SAL)
31 ---------- --------- ----------
32         10 CLERK           1400
33         10 MANAGER         2450
34         10 PRESIDENT       5000
35         10                 8850
36         20 ANALYST         3000
37         20 CLERK            800
38         20 MANAGER         2975
39         20                 6775
40         30 CLERK            950
41         30 MANAGER         2850
42         30 SALESMAN        5600
43         30                 9400
44                           25025
45
46 13 rows selected