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row_number() over(partition by 分组列 order by 排序列 desc)

热度:88   发布时间:2023-09-06 22:38:46.0

语法格式:row_number() over(partition by 分组列 order by 排序列 desc)

row_number() over()分组排序功能:

在使用 row_number() over()函数时候,over()里头的分组以及排序的执行晚于 where 、group by、 order by 的执行。

例一:

表数据:

create table TEST_ROW_NUMBER_OVER(id varchar(10) not null,name varchar(10) null,age varchar(10) null,salary int null
);
select * from TEST_ROW_NUMBER_OVER t;insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(1,'a',10,8000);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(1,'a2',11,6500);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(2,'b',12,13000);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(2,'b2',13,4500);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(3,'c',14,3000);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(3,'c2',15,20000);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(4,'d',16,30000);
insert into TEST_ROW_NUMBER_OVER(id,name,age,salary) values(5,'d2',17,1800);

一次排序:对查询结果进行排序(无分组)

select id,name,age,salary,row_number()over(order by salary desc) rn
from TEST_ROW_NUMBER_OVER t

结果:
row_number() over(partition by 分组列 order by 排序列 desc)
进一步排序:根据id分组排序

select id,name,age,salary,row_number()over(partition by id order by salary desc) rank
from TEST_ROW_NUMBER_OVER t

结果:
row_number() over(partition by 分组列 order by 排序列 desc)
再一次排序:找出每一组中序号为一的数据

select * from(select id,name,age,salary,row_number()over(partition by id order by salary desc) rank
from TEST_ROW_NUMBER_OVER t)
where rank <2

结果:
row_number() over(partition by 分组列 order by 排序列 desc)
排序找出年龄在13岁到16岁数据,按salary排序

select id,name,age,salary,row_number()over(order by salary desc)  rank
from TEST_ROW_NUMBER_OVER t where age between '13' and '16'

结果:结果中 rank 的序号,其实就表明了 over(order by salary desc) 是在where age between and 后执行的
row_number() over(partition by 分组列 order by 排序列 desc)
例二:

1.使用row_number()函数进行编号,如

select email,customerID, ROW_NUMBER() over(order by psd) as rows from QT_Customer

原理:先按psd进行排序,排序完后,给每条数据进行编号。

2.在订单中按价格的升序进行排序,并给每条记录进行排序代码如下:

select DID,customerID,totalPrice,ROW_NUMBER() over(order by totalPrice) as rows from OP_Order

3.统计出每一个各户的所有订单并按每一个客户下的订单的金额 升序排序,同时给每一个客户的订单进行编号。这样就知道每个客户下几单了:

select ROW_NUMBER() over(partition by customerID  order by totalPrice)as rows,customerID,totalPrice, DID from OP_Order

4.统计每一个客户最近下的订单是第几次下的订单:

with tabs as  
(  
select ROW_NUMBER() over(partition by customerID  order by totalPrice)as rows,customerID,totalPrice, DID from OP_Order  )  
select MAX(rows) as '下单次数',customerID from tabs 
group by customerID 

5.统计每一个客户所有的订单中购买的金额最小,而且并统计改订单中,客户是第几次购买的:

思路:利用临时表来执行这一操作。

1.先按客户进行分组,然后按客户的下单的时间进行排序,并进行编号。

2.然后利用子查询查找出每一个客户购买时的最小价格。

3.根据查找出每一个客户的最小价格来查找相应的记录。

with tabs as  (  select ROW_NUMBER() over(partition by customerID  order by insDT) as rows,customerID,totalPrice, DID from OP_Order  )  select * from tabs  where totalPrice in   (  select MIN(totalPrice)from tabs group by customerID  ) 

6.筛选出客户第一次下的订单。

思路。利用rows=1来查询客户第一次下的订单记录。

  with tabs as  (  select ROW_NUMBER() over(partition by customerID  order by insDT) as rows,* from OP_Order  )  select * from tabs where rows = 1 select * from OP_Order 

7.注意:在使用over等开窗函数时,over里头的分组及排序的执行晚于“where,group by,order by”的执行。

 select   ROW_NUMBER() over(partition by customerID  order by insDT) as rows,  customerID,totalPrice, DID  

本文转载自:https://blog.csdn.net/qq_25221835/article/details/82762416

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