SQL之统计

单表统计

select count(*) from emp;
select job,sum(sal),count(*) from emp group by job;
select deptno,max(hiredate),min(hiredate) from emp group by deptno;
select trunc(hiredate,'yyyy'),count(distinct deptno),count(*) from emp group by trunc(hiredate,'yyyy');
select deptno,listagg(ename,',')within group(order by empno) from emp group by deptno;
select deptno,cast(listagg(ename,',')within group(order by empno) as varchar(50)) namelist from emp group by deptno;

 

 

多表关联统计

select * from salgrade;
select emp.*,grade from emp,salgrade;
select grade,sum(sal) from emp,salgrade group by grade;
select emp.*,grade from emp,salgrade where sal between losal and hisal;
select grade,sum(sal) from emp,salgrade where sal between losal and hisal group by grade;
select deptno,count(*),count(empno) from emp right join dept using(deptno) group by deptno;
select dept.deptno,count(*),count(empno) from emp right join dept on emp.deptno=dept.deptno group by dept.deptno;
select e.deptno,grade,min(sal),max(sal) from emp e,salgrade s,dept d where sal between losal and hisal and e.deptno=d.deptno group by e.deptno,grade order by 1,2;
select e.deptno,min(sal),max(sal) from emp e,salgrade s,dept d where sal between losal and hisal and e.deptno=d.deptno group by e.deptno order by 1;
select e.deptno,min(sal),max(sal) from emp e,salgrade s,dept d where sal between losal and hisal and e.deptno=d.deptno group by e.deptno,grade order by 1,2;

 固定行列转换

 

 

 

create table shigu(
sjname    varchar2(20),
yuefeng   varchar2(10),
sgsl      number);

insert into shigu values('司机张','三月',1);
insert into shigu values('司机刘','一月',2);
insert into shigu values('司机刘','二月',1);
commit;
insert into shigu values('司机张','二月',2);

select * from shigu;
select sjname,Decode(yuefeng,'一月',sgsl,0) m1,Decode(yuefeng,'二月',sgsl,0) m2,Decode(yuefeng,'三月',sgsl,0) m3 from shigu;
select sjname, max(m1), max(m2), max(m3)
  from (select sjname,
               Decode(yuefeng, '一月', sgsl, 0) m1,
               Decode(yuefeng, '二月', sgsl, 0) m2,
               Decode(yuefeng, '三月', sgsl, 0) m3
          from shigu)
 group by sjname;

 

分组求和统计

 

 

 

 

 

 

select e.deptno,grade,count(*) from emp e,salgrade s where sal between losal and hisal group by rollup(e.deptno,grade) order by deptno,grade;

 

 

 

select e.deptno,grade,count(*) from emp e,salgrade s where sal between losal and hisal group by cube(e.deptno,grade) order by deptno,grade;

 

 

 

select e.deptno,grade,count(*) from emp e,salgrade s where sal between losal and hisal group by e.deptno,rollup(grade) order by deptno,grade;

 

 

下面这个链接总结的不错 

http://blog.sina.com.cn/s/blog_7e04e0d00101g6jb.html

只按部门编号和只按薪水等级统计人数

select e.deptno,grade,count(*) from emp e,salgrade s where sal between losal and hisal group by grouping sets(e.deptno,grade) order by deptno,grade;