Oracle 高级排序函数 和 高级分组函数

高级排序函数: 
[ ROW_NUMBER()| RANK() | DENSE_RANK ] OVER (partition by xx order by xx)


1.row_number() 连续且递增的数字 1 2 3 4 
  row_number() over (partition by xx order by xx )  
  
--学生表中按照所在专业分组，同专业内按成绩倒序排序，成绩相同则按学号正序排序，并给予组内等级
select row_number() over(partition by class_id order by score desc)rn,t.* from student2016 t
  
2.rank() 跳跃排序 若有相同数据则排名相同 然后跳跃排序 1 2 2 2 5
  rank() over (partition by xx order by xx ) 


select rank() over(partition by class_id order by score desc)rn,t.* from student2016 t
  
3.dense_rank 若有相同数据则排名相同 然后递增排序
dense_rank  over (partition by xx order by xx ) 1 2 2 2 3


select dense_rank() over(partition by class_id order by score desc)rn,t.* from student2016 t

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高级分组函数

group by rollup(a,b,c)

select a，b,c,sum(d) from test group by rollup(a,b,c)

对rollup后面的列 按从右到左以少一列的方式进行分组直到所有列都去掉后的分组（也就是全表分组）
对于n个参数的 rollup，有n+1次分组

即按a，b，c，分组，union all a，b分组 union all a分组 union from test

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group by cube(a,b,c)

对n个参数，有2^n次分组

即按 ab，ac，a，bc，b，c最后对 全部分组

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group by grouping sets(a,b)

即只列出 对 a分组后，和对 b分组的结果集

-- 创建销售表
create table sales_tab(
year_id number not null,
month_id number not null,
day_id number not null,
sales_value number(10,2) not null
);

-- 插入数据
insert into sales_tab
select trunc(dbms_random.value(low=>2010,high=>2012)) as year_id,
trunc(dbms_random.value(low=>1,high=>13)) as month_id,
trunc(dbms_random.value(low=>1,high=>32)) as day_id,
round(dbms_random.value(low=>1,high=>100)) as sales_value
from dual 
connect by level <=1000;

-- 查询 group by 后的数据 
select sum(t.sales_value) from SALES_TAB t -- 1行

select t.year_id,t.month_id,t.day_id,sum(t.sales_value) sales from SALES_TAB t group by t.year_id,t.month_id,t.day_id 
order by t.year_id,t.month_id,t.day_id desc; -- 540行

select t.year_id,t.month_id,sum(t.sales_value) sales from SALES_TAB t group by t.year_id,t.month_id
order by t.year_id,t.month_id desc; -- 24 行

select t.year_id,sum(t.sales_value) sales from SALES_TAB t group by t.year_id
order by t.year_id desc; -- 2 行

-- 使用高级分组函数
-- group by rollup（a,b,c）
select t.year_id,t.month_id,t.day_id,sum(t.sales_value) sales from SALES_TAB t group by rollup(t.year_id,t.month_id,t.day_id)
order by t.year_id,t.month_id,t.day_id; -- 567 行 = 同上面 1+540+24+2

-- group by cube(a,b,c)
select t.year_id,t.month_id,t.day_id,sum(t.sales_value) sales from SALES_TAB t group by cube(t.year_id,t.month_id,t.day_id)
order by t.year_id,t.month_id,t.day_id;

--group by grouping sets(a,b,c) 
select t.year_id,t.month_id,sum(t.sales_value) sales from SALES_TAB t group by cube(t.year_id,t.month_id)
order by 1,2; -- 39 行

select t.year_id,t.month_id,sum(t.sales_value) sales from SALES_TAB t group by grouping sets(t.year_id,t.month_id)
order by 1,2; -- 14 行