Question

假设在SQL Server上有一个包含EMPLOYEE列的表ID (int), Name (nvarchar), Surname(nvarchar)。

这就是你所知道的全部。您无法在表格中看到数据。

您被命令只删除一个名为“Alice”的记录。

您如何撰写适当的查询？

Answer 1

DELETE TOP (1)
FROM EMPLOYEE 
WHERE Name='Alice'

Answer 2

DELETE TOP (1) FROM EMPLOYEE WHERE Name = 'Alice'

Answer 3

在SQL Server中：

DELETE TOP 1 FROM EMPLOYEE WHERE Name = 'Alice'

Answer 4

这里建议的所有答案都是相似的，只要您介绍问题，所有这些答案都是最佳的。

但这会强制您的代码删除Name ='Alice'的第一条记录。但是如果你需要有一点额外的力量来选择哪个'Alice'要删除，如果你的表中有多个。但当然，ID必须是Primary Key或Unique

SELECT FROM EMPLOYEE ID, Surname WHERE Name = 'Alice'

这将显示结果，然后您可以将要删除的目标记录的ID放入以下查询（假设您要删除的记录的ID为56）

DELETE FROM EMPLOYEE  WHERE ID = 56

Answer 5

declare @Holder table ( EmployeeKey int , Name varchar(24) , Surname varchar(24) )


Insert into @Holder ( EmployeeKey , Name , Surname )
            select 201 , 'Alice' , 'Smith'
union all   select 102 , 'Mary' , 'Smith'
union all   select 203 , 'Alice' , 'Henderson'
union all   select 104 , 'John' , 'Smith'
union all   select 105 , 'Paul' , 'Johnson'
union all   select 206 , 'Alice' , 'Jones'

Delete @Holder
/*  Select * ............. while debugging, you can remove the 'Delete @Holder' and put in a 'Select *' to see the results (of what ~will be deleted) */
From 
@Holder h
join 
(select top 1 EmployeeKey from @Holder innerH where Name = 'Alice' /* order by EmployeeKey DESC */ ) as derived1
 on h.EmployeeKey = derived1.EmployeeKey

select * from @Holder order by Name , EmployeeKey

/*
order by EmployeeKey DESC is optional, aka, if you want to "prefer" which one gets popped for delete, you can tweak it as needed
*/

仅删除SQL Server上的一条记录

5 个答案: