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