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Oracle分组函数之ROLLUP用法

2019-07-03  本文已影响17人  smileNicky

rollup函数
本博客简单介绍一下oracle分组函数之rollup的用法,rollup函数常用于分组统计,也是属于oracle分析函数的一种

环境准备

create table dept as select * from scott.dept;
create table emp as select * from scott.emp;

业务场景:求各部门的工资总和及其所有部门的工资总和

这里可以用union来做,先按部门统计工资之和,然后在统计全部部门的工资之和


select a.dname, sum(b.sal)
  from scott.dept a, scott.emp b
 where a.deptno = b.deptno
 group by a.dname
union all
select null, sum(b.sal)
  from scott.dept a, scott.emp b
 where a.deptno = b.deptno;

上面是用union来做,然后用rollup来做,语法更简单,而且性能更好


select a.dname, sum(b.sal)
  from scott.dept a, scott.emp b
 where a.deptno = b.deptno
 group by rollup(a.dname);
在这里插入图片描述

业务场景:基于上面的统计,再加需求,现在要看看每个部门岗位对应的工资之和

select a.dname, b.job, sum(b.sal)
  from scott.dept a, scott.emp b
 where a.deptno = b.deptno
 group by a.dname, b.job
union all//各部门的工资之和
select a.dname, null, sum(b.sal)
  from scott.dept a, scott.emp b
 where a.deptno = b.deptno
 group by a.dname
union all//所有部门工资之和
select null, null, sum(b.sal)
  from scott.dept a, scott.emp b
 where a.deptno = b.deptno;

用rollup实现,语法更简单

select a.dname, b.job, sum(b.sal)
  from scott.dept a, scott.emp b
 where a.deptno = b.deptno
 group by rollup(a.dname, b.job);
在这里插入图片描述

假如再加个时间统计的,可以用下面sql:

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

cube函数

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

在这里插入图片描述

cube函数是维度更细的统计,语法和rollup类似

假设有n个维度,那么rollup会有n个聚合,cube会有2n个聚合

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