【SQL】ROW_NUMBER() OVER(partition by 分组列 order by 排序列)用法详解+经典实例
#用法说明
select row_number() over(partition by A order by B ) as rowIndex from table
A :为分组字段
B:为分组后的排序字段。
table 表的结构 多为: 多人 多条的相关数据。(比如:订单信息)
此条sql语句,多用于对数据进行分组排序,并对每个组中的数据分别进行编号,编号从1开始递增,每个组内的编号不会重复;
#经典实例
0、填充数据
1 create table [OrderInfo]( 2 [Id] [int] PRIMARY KEY IDENTITY(1,1) NOT NULL, 3 [UserId] [nvarchar](50) NOT NULL, 4 [TotalPrice] [float] NOT NULL, 5 [OrderTime] [datetime] NOT NULL, 6 ); 7 8 INSERT INTO [dbo].[OrderInfo] 9 ([UserId] 10 ,[TotalPrice] 11 ,[OrderTime]) 12 VALUES 13 (N'1', 111, CAST(N'2011-01-01' AS DateTime)), 14 (N'1', 112, CAST(N'2011-01-02' AS DateTime)), 15 (N'3', 311, CAST(N'2013-01-01' AS DateTime)), 16 (N'3', 312, CAST(N'2013-01-02' AS DateTime)), 17 (N'2', 211, CAST(N'2012-01-01' AS DateTime)), 18 (N'2', 212, CAST(N'2012-01-02' AS DateTime)), 19 (N'1', 113, CAST(N'2011-01-03' AS DateTime)), 20 (N'2', 213, CAST(N'2012-01-03' AS DateTime)), 21 (N'3', 313, CAST(N'2013-01-03' AS DateTime)) 22 GO
1、使用row_number()函数对订单进行编号,按照订单时间倒序。(此需求多用于分页)
1 select Id,UserId,TotalPrice,OrderTime,ROW_NUMBER() over (order by OrderTime desc) as rowIndex from OrderInfo
#分页场景:每页3条数据,取第2页
1 with 2 baseDate 3 as 4 ( 5 select Id,UserId,TotalPrice,OrderTime,ROW_NUMBER() over (order by OrderTime desc) as rowIndex from OrderInfo 6 ) 7 select * from baseDate where rowIndex>3 and rowIndex<7
2、所有订单按照客户进行分组,并按照客户下的订单的金额倒序排列。
1 select Id,UserId,orderTime,ROW_NUMBER() over(partition by UserId order by TotalPrice desc) as rowIndex from OrderInfo
3、筛选出客户第一次下的订单。
思路:利用rowIndex来判断订单是客户第几次下单;
1 with 2 baseDate 3 as 4 ( 5 select Id,UserId,TotalPrice,orderTime,ROW_NUMBER() over (partition by UserId order by orderTime) as rowIndex from OrderInfo 6 ) 7 select * from baseDate where rowIndex=1
4、筛选出客户在‘2011年1月1日之后的第一次下的订单。
思路:在分组排序之前进行实践筛选;
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。
1 with 2 baseDate 3 as 4 ( 5 select Id,UserId,TotalPrice,orderTime,ROW_NUMBER() over (partition by UserId order by orderTime) as rowIndex from OrderInfo 6 where OrderTime>'2011-1-1' 7 ) 8 select * from baseDate where rowIndex=1
5、只保留每个客户的最近的一次订单,其余的订单删掉。(常用于删除重复数据)
1 with 2 baseDate 3 as 4 ( 5 select Id,UserId,TotalPrice,OrderTime,ROW_NUMBER()over (partition by UserId order by OrderTime desc) as rowIndex from OrderInfo 6 ) 7 delete from baseDate where rowIndex <> 1
6、统计每一个客户所有的订单中金额最大,并统计该订单是客户第几次购买;
思路:
1)先按照客户进行分组,然后按照客户下单的时间进行正序排列,并编号(rowIndex),生成临时表baseDate;
2)再按照客户进行分组,然后按照客户下单的金额进行倒序排列,并编号(rowIndex),生成临时表basePrice;
3)最后取basePrice中编号为1的数据,然后根据id到baseDate中去查,即可;
1 with 2 baseDate 3 as 4 ( 5 select Id,UserId,TotalPrice,orderTime,ROW_NUMBER() over (partition by UserId order by orderTime) as rowIndex from OrderInfo 6 ), 7 basePrice 8 as 9 ( 10 select Id,UserId,orderTime,ROW_NUMBER() over(partition by UserId order by TotalPrice desc) as rowIndex from OrderInfo 11 ) 12 select * from baseDate 13 where Id in ( 14 select Id from basePrice where rowIndex=1 15 )
#图中的rowIndex字段就是该订单是第几次购买;
作者:willingtolove
出处:http://www.cnblogs.com/willingtolove/
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