在日常的项目开发当中,经常会遇到获取同一属性相同的记录,如何获取记录时间最新的那一条,比如获取某个淘宝用户最新一次的购物记录,美团外卖获取用户最后一次的点外卖记录等等场景,下面通过简单的示例给大家提供三种比较常见的SQL写法,希望能给大家带来一些思路。 1、建表脚本:记录的是当前用户的订单记录。如果某个人多次下单会出现某个人重复下订单的记录。脚本如下: CREATE TABLE [dbo].[t_expense_record_info]( [id] [int] IDENTITY(1,1) NOT NULL, [goods_id] [int] NULL, [amount] [decimal](18, 6) NULL, [expense_time] [datetime] NULL, [user_id] [int] NULL, [create_date] [datetime] NULL, CONSTRAINT [PK_t_expense_record_info] PRIMARY KEY CLUSTERED ( [id] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO SET IDENTITY_INSERT [dbo].[t_expense_record_info] ON INSERT [dbo].[t_expense_record_info] ([id], [goods_id], [amount], [expense_time], [user_id], [create_date]) VALUES (1, 100, CAST(5000.000000 AS Decimal(18, 6)), CAST(0x0000A9D900CDFE60 AS DateTime), 1, CAST(0x0000AB4700000000 AS DateTime)) INSERT [dbo].[t_expense_record_info] ([id], [goods_id], [amount], [expense_time], [user_id], [create_date]) VALUES (2, 100, CAST(2000.000000 AS Decimal(18, 6)), CAST(0x0000AB460130DEE0 AS DateTime), 2, CAST(0x0000AB4700000000 AS DateTime)) INSERT [dbo].[t_expense_record_info] ([id], [goods_id], [amount], [expense_time], [user_id], [create_date]) VALUES (3, 118, CAST(300.000000 AS Decimal(18, 6)), CAST(0x0000AB430130DEE0 AS DateTime), 1, CAST(0x0000AB4700000000 AS DateTime)) INSERT [dbo].[t_expense_record_info] ([id], [goods_id], [amount], [expense_time], [user_id], [create_date]) VALUES (4, 20, CAST(1500.000000 AS Decimal(18, 6)), CAST(0x0000AB480130DEE0 AS DateTime), 2, CAST(0x0000AB4700000000 AS DateTime)) INSERT [dbo].[t_expense_record_info] ([id], [goods_id], [amount], [expense_time], [user_id], [create_date]) VALUES (5, 300, CAST(100.000000 AS Decimal(18, 6)), CAST(0x0000AA860130DEE0 AS DateTime), 3, CAST(0x0000AB4700000000 AS DateTime)) INSERT [dbo].[t_expense_record_info] ([id], [goods_id], [amount], [expense_time], [user_id], [create_date]) VALUES (6, 80, CAST(7000.000000 AS Decimal(18, 6)), CAST(0x0000AAD5013BDB60 AS DateTime), 1, CAST(0x0000AB4700000000 AS DateTime)) SET IDENTITY_INSERT [dbo].[t_expense_record_info] OFF EXEC sys.sp_addextendedproperty @name=N'MS_Description', @value=N'主键' , @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE',@level1name=N't_expense_record_info', @level2type=N'COLUMN',@level2name=N'id' GO EXEC sys.sp_addextendedproperty @name=N'MS_Description', @value=N'商品id' , @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE',@level1name=N't_expense_record_info', @level2type=N'COLUMN',@level2name=N'goods_id' GO EXEC sys.sp_addextendedproperty @name=N'MS_Description', @value=N'消费金额' , @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE',@level1name=N't_expense_record_info', @level2type=N'COLUMN',@level2name=N'amount' GO EXEC sys.sp_addextendedproperty @name=N'MS_Description', @value=N'消费时间' , @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE',@level1name=N't_expense_record_info', @level2type=N'COLUMN',@level2name=N'expense_time' GO EXEC sys.sp_addextendedproperty @name=N'MS_Description', @value=N'消费者id' , @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE',@level1name=N't_expense_record_info', @level2type=N'COLUMN',@level2name=N'user_id' GO EXEC sys.sp_addextendedproperty @name=N'MS_Description', @value=N'创建时间' , @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE',@level1name=N't_expense_record_info', @level2type=N'COLUMN',@level2name=N'create_date' GO EXEC sys.sp_addextendedproperty @name=N'MS_Description', @value=N'消费记录表' , @level0type=N'SCHEMA',@level0name=N'dbo', @level1type=N'TABLE',@level1name=N't_expense_record_info' GO SELECT * FROM t_expense_record_info ORDER BY user_id; 执行SQL查询结果如下图: 方法1: SELECT a.* FROM t_expense_record_info a LEFT JOIN t_expense_record_info b ON a.user_id = b.user_id AND a.expense_time < b.expense_time WHERE b.id IS NULL ORDER BY a.user_id; 方法2: select * from t_expense_record_info a where a.expense_time in (select max(b.expense_time) from t_expense_record_info b where b.user_id=a.user_id) ORDER BY a.user_id; 方法3: select * from t_expense_record_info a where not exists (select 1 from t_expense_record_info b where b.user_id=a.user_id and b.expense_time>a.expense_time) ORDER BY a.user_id; 最终执行结果如图: |
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