Question

我想删除特定列

上具有最高值的行

（我知道有答案，但由于某些原因，它们都不适合我）

我在visual studio c＃中使用SQL

进行的所有编码

MyDatabase：hours

Hours_Left | Hours_Spent | Time_Written | Mode | Time_Start | Time_End | Index
==============================================================================
aa         | bb          | cc           | dd   | ee         | ff       | 3
gg         | hh          | ii           | jj   | kk         | ll       | 4
mm         | nn          | oo           | pp   | qq         | rr       | 5
ss         | tt          | uu           | vv   | ww         | xx       | 6

[Hours_Left]   VARCHAR (MAX) NULL,
[Hours_Spent]  VARCHAR (MAX) NULL,
[Time_Written] VARCHAR (MAX) NULL,
[Mode]         VARCHAR (MAX) NULL,
[Time_Start]   VARCHAR (MAX) NULL,
[Time_End]     VARCHAR (MAX) NULL,
[Index]        INT           IDENTITY (1, 1) NOT NULL

我的代码：

if (con.State != ConnectionState.Open)
        {
            con.Close();
            con.Open();
        }
        SqlCommand cmd = con.CreateCommand();
        cmd.CommandType = CommandType.Text;
        cmd.CommandText = @"DELETE FROM hours WHERE Index = select max(Index) from hours limit 1";
        cmd.ExecuteNonQuery();
        con.Close();
        Display_Data();

在commandText

时不能工作

@"DELETE TOP(1) FROM hours
  WHERE Index in 
  (SELECT TOP(1) Index FROM hours
  ORDER BY Index DESC);";

我想删除最高索引的整行 - 即删除索引为6的行，它是最高索引

错误：

cmd.ExecuteNonQuery();

错误是：

System.Data.SqlClient.SqlException：＆＃39;＆＃39; Index＆＃39;附近的语法不正确。如果这是作为表提示的一部分，一个WITH关键字和现在需要括号。请参阅SQL Server联机丛书语法。

Answer 1

索引是关键字，您需要使用[Index]。

Answer 2

尝试

 delete from hours where Index = max(index);

Answer 3

如“ajg”所述，第二个查询中的问题是使用保留关键字Index使用方括号来转义关键字

更好的方法是使用CTE

;with cte as
(
select top (1) * from hours order by [Index] desc
)
delete from cte

Answer 4

试试这个;

delete x
from dbo.[Hours] x
where exists(select 1 from dbo.[Hours] xx having MAX(xx.[Index])=x.[Index])

Answer 5

在SQL Server中，您可以执行以下操作：

DELETE h
    FROM hours h
    WHERE h.Index = (select max(h2.Index) from hours h2) ;

如果您担心index可能有重复项，请将delete与top一起使用。

Answer 6

这应该有用;

DELETE FROM hours 
WHERE Index = max(index);

Answer 7

  delete from hours where [Index] = (select max([Index]) from hours)

我猜你错过了括号。

Answer 8

 delete from tablename 
 where columnname = 
 ( select dummytable.maxVal from 
    (select max(columnname) as maxVal from tablename) 
   dummytable
 );

删除具有特定列

8 个答案: