TSQL - 每组删除除 1 之外的所有行

Posted 2023-03-29

【中文标题】TSQL - 每组删除除 1 之外的所有行

【英文标题】：TSQL - Delete All Rows Except 1 Per Group

【发布时间】：2016-03-08 02:56:17

【问题描述】：

假设我有 5 个工作中心（工作中心 1、工作中心 2、工作中心 3、工作中心 4、工作中心 5）

每个工作中心都有几行按数据输入日期排序的注释。我想删除每个工作中心的所有行，最后输入的数据行除外。

如果我的列是：ID |工作中心 |注意 |日志_日期

我该怎么做呢？

我的代码只为我提供了整个表格的最新注释条目，但我希望每个工作中心都有一个。

这就是我现在拥有的：

DELETE FROM @Table
WHERE ID NOT IN (SELECT TOP 1 ID FROM @Table 
             GROUP BY Workcenter, ID 
             ORDER BY Log_Date DESC)

【参考方案1】：

试试这个：

delete t1 from table t1 
where not exists
(select 1 from 
       (select workcenter,max(log_date)as log_date from table group by workcenter) t2  
       where t1.workcenter = t2.workcenter and t1.log_date = t2.log_date
)

使用 exists 子查询获取每个工作中心的最大 log_date，然后将它们连接到表。

【讨论】：

正是我需要的。谢谢。

【参考方案2】：

using CTE we can achieve this:

;WITH cte AS
(SELECT ROW_NUMBER() OVER (PARTITION BY name ORDER BY createdate DESC ) AS rowno, * FROM workgroups)
DELETE FROM cte WHERE rowno !=1;

CREATE TABLE workgroups(id INT IDENTITY(1,1),name VARCHAR(50), createdate DATETIME DEFAULT GETDATE())

INSERT [dbo].[workgroups] ([id], [name], [createdate]) VALUES (1, N'workgroup1', CAST(0x0000A60F011F7840 AS DateTime))
INSERT [dbo].[workgroups] ([id], [name], [createdate]) VALUES (2, N'workgroup1', CAST(0x0000A60F011F7F8E AS DateTime))
INSERT [dbo].[workgroups] ([id], [name], [createdate]) VALUES (3, N'workgroup1', CAST(0x0000A60F011F8728 AS DateTime))
INSERT [dbo].[workgroups] ([id], [name], [createdate]) VALUES (4, N'workgroup2', CAST(0x0000A60F011F92B9 AS DateTime))
INSERT [dbo].[workgroups] ([id], [name], [createdate]) VALUES (5, N'workgroup2', CAST(0x0000A60F011F97C0 AS DateTime))
INSERT [dbo].[workgroups] ([id], [name], [createdate]) VALUES (6, N'workgroup3', CAST(0x0000A60F011FA443 AS DateTime))
INSERT [dbo].[workgroups] ([id], [name], [createdate]) VALUES (7, N'workgroup3', CAST(0x0000A60F011FA73B AS DateTime))
INSERT [dbo].[workgroups] ([id], [name], [createdate]) VALUES (8, N'workgroup3', CAST(0x0000A60F011FA9FB AS DateTime))

SELECT ROW_NUMBER() OVER (PARTITION BY name ORDER BY createdate DESC ) AS rowno, * FROM workgroups


;WITH cte AS
(SELECT ROW_NUMBER() OVER (PARTITION BY name ORDER BY createdate DESC ) AS rowno, * FROM workgroups)
DELETE FROM cte WHERE rowno !=1;