当我们在做报表统计的时候，很多时候需要用到‘合计’这个功能，比如我们想得到如下格式的报表：
这张表是按照deptno分组，然后按照deptno分组合计。rollup函数可以完美的解决这个问题。
1.建立一张t表：
create table T
(
empno NUMBER(4),
ename VARCHAR2(10),
job VARCHAR2(9),
sal NUMBER(7,2),
comm NUMBER(7,2),
deptno NUMBER(2)
);
2.插入数据：
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7844, 'TURNER', 'SALESMAN', 1500.00, 0.00, 30);
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7499, 'ALLEN', 'SALESMAN', 1600.00, 300.00, 30);
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7521, 'WARD', 'SALESMAN', 1250.00, 500.00, 30);
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7566, 'JONES', 'MANAGER', 2975.00, 100.00, 20);
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7654, 'MARTIN', 'SALESMAN', 1250.00, 1400.00, 30);
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7698, 'BLAKE', 'MANAGER', 2850.00, 100.00, 30);
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7782, 'CLARK', 'MANAGER', 2450.00, 100.00, 10);
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7788, 'SCOTT', 'ANALYST', 3000.00, 100.00, 20);
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7839, 'KING', 'PRESIDENT', 5000.00, 100.00, 10);
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7876, 'ADAMS', 'CLERK', 1100.00, 100.00, 20);
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7900, 'JAMES', 'CLERK', 950.00, 100.00, 30);
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7902, 'FORD', 'ANALYST', 3000.00, 100.00, 20);
insert into t (EMPNO, ENAME, JOB, SAL, COMM, DEPTNO)
values (7934, 'MILLER', 'CLERK', 1300.00, 100.00, 10);
commit;
3.使用rollup函数
select empno, ename, sum(sal) as sal, sum(comm) as comm, deptno
from t
group by rollup(deptno, (empno, ename))
having grouping(deptno) = 0;