【oracle】【sql】oracle分组

20150225_Oracle_分组.sql
参考:
http://wenku.baidu.com/view/225568538bd63186bdebbc23.html

--1. group by rollup语句 与 group by语句
--写法1
select
brand_code,code_id,count(*)
from t_test
group by rollup (brand_code,code_id);
--写法2
select
brand_code,code_id,count(*)
from t_test
group by rollup ((brand_code,code_id));
说明: rollup ((brand_code,code_id)) 而不是 rollup (brand_code,code_id)，表示 把 (brand_code,code_id) 作为一个整体，即只考虑 要么都非空，要么都为空的情况。

--2. grouping 函数
select
brand_code,code_id,count(id),
grouping(brand_code),
grouping(code_id)
from t_test
group by rollup(brand_code,code_id);

--3. group by grouping sets语句
城市+水果 的 均价
季节+水果 的 均价

create table t_fruit(
season varchar2(50),
city varchar2(100),
fruit varchar2(50),
price number(5,2)
);

--写法1
select null season,city,fruit,round(avg(price),2)
from t_fruit
group by city,fruit
union all
select season,null city,fruit,round(avg(price),2)
from t_fruit
group by season,fruit;

--写法2
select season,city,fruit,round(avg(price),2)
from t_fruit
group by grouping sets ((city,fruit),(season,fruit));