标签：table 保留 排列 删除重复数据 oat 16px 序列 datetime 详解
原文:【SQL】ROW_NUMBER() OVER(partition by 分组列 order by 排序列)用法详解+经典实例
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；
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 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
1 select Id,UserId,orderTime,ROW_NUMBER() over(partition by UserId order by TotalPrice desc) as rowIndex from OrderInfo
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
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
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
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；
【SQL】ROW_NUMBER() OVER(partition by 分组列 order by 排序列)用法详解+经典实例
标签：table 保留 排列 删除重复数据 oat 16px 序列 datetime 详解
原文地址：https://www.cnblogs.com/lonelyxmas/p/10652413.html
