MYSQL row_number()与over()函数用法详解

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:

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:

 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:

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

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  
    from op_order where insdt>'2011-07-22' 

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