扩展的group by的函数还是要符合group by的相关语法语义规则,比如select中不能直接显示非分组列
rollup
oracle使用rollup对group by进行扩展,他允许计算标准分组及相应维度的小计合计
select group by rollup(grouping_column_reference_list)
先计算标准分组,然后列从右到左递减计算更高一级的小计,一直到列全部被选完,最后计算合计
select a.dname,b.job,sum(b.sal)
from dept a,emp b
where a.deptno=b.deptno
group by a.dname,b.job
union all
select a.dname,null,sum(b.sal)
from dept a,emp b
where a.deptno=b.deptno
group by a.dname
union all
select null,null,sum(b.sal)
from dept a,emp b
where a.deptno=b.deptno;
select a.dname,b.job,sum(b.sal) sum_sal
from dept a,emp b
where a.deptno=b.deptno
group by rollup(a.dname,b.job)
select to_char(b.hiredate,'yyyy') hire_year,a.dname,b.job,sum(b.sal) sum_sal
from dept a,emp b
where a.deptno=b.deptno
group by rollup(to_char(b.hiredate,'yyyy'),a.dname,b.job);
部分rollup分组
select to_char(b.hiredate,'yyyy') hire_year,a.dname,b.job,sum(b.sal) sum_sal
from dept a,emp b
where a.deptno=b.deptno
group by to_char(b.hiredate,'yyyy'),a.dname, rollup(b.job);
rollup中指定n列,分组方式就有n+1种,如果部分rollup可以剔除某些不需要的小计和合计,只要根据需求将相关的列从rollup中移出,放到group by 中即可
CUBE
可以对不同维度的所有可能分组进行统计,从而生成交叉报表
select ---- group by cube(grouping_column_reference_list)
select b.job,a.dname,sum(b.sal)
from dept a,emp b
where a.deptno=b.deptno
group by cube(a.dname,b.job)
部分cube
select a.dname,b.job,sum(b.sal)
from dept a,emp b
where a.deptno=b.deptno
group by a.dname,cube(b.job);
cube实现了多维组的分析统计工作
grouping sets
只有指定某些维度的小计,没有常规分组结果及合计结果,只对关注某些维度的小计分析很有用
select .... group by grouping sets(grouping_column_reference_list)
select to_char(b.hiredate,'yyyy') hie_year,a.dname,b.job,sum(b.sal) sum_sal
from dept a,emp b
where a.deptno=b.deptno
group by grouping sets(to_char(b.hiredate,'yyyy'),a.dname,b.job);
部分grouping sets
select to_char(b.hiredate,'yyyy') hie_year,a.dname,b.job,sum(b.sal) sum_sal
from dept a,emp b
where a.deptno=b.deptno
group by a.dname, grouping sets(to_char(b.hiredate,'yyyy'),b.job);
cube ,rollup 作为grouping sets的参数
grouping sets 只对单列进行分组,而不提供合计的功能,如果需要提供合计的功能,那么就可以使用rollup或者cube作为grouping sets的参数
select a.dname,b.job,sum(b.sal)
from dept a,emp b
where a.deptno=b.deptno
group by grouping sets(rollup( a.dname),rollup(b.job));