Sql 将查询值赋给变量

帮助，我使用SQL Server作为我的数据库，我的后端是VB.NET

我要分配此查询的值：

SELECT sum(productPrice) from cartTbl

，然后将该值赋给名为

totalPrice

的文本框

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如何执行此操作？提前谢谢你

如果使用

然后可以调用此方法来获取价格

Dim prodPrice = GetProductPrice()

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如果使用，则应使用

ExecuteScalar（）

然后可以调用此方法来获取价格

Dim prodPrice = GetProductPrice()

你可以用

SELECT @var1=sum(productPrice) from cartTbl

你可以用

SELECT @var1=sum(productPrice) from cartTbl

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为计算列使用别名

 SELECT sum(productPrice) as prod_sum
 from cartTbl

然后你可以这样读

While dr.Read()     
     totalPrice.Text = dr("prod_sum")
End While

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为计算列使用别名

 SELECT sum(productPrice) as prod_sum
 from cartTbl

然后你可以这样读

While dr.Read()     
     totalPrice.Text = dr("prod_sum")
End While

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它就这么简单，但请阅读一些基本信息

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它就这么简单，但请阅读一些基本信息

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要扩展已经说过的内容，您可以使用以下方法使其更加灵活：

Private Sub Test()
    'Get/set connection string
    Me.TextBox1.Text = Me.SQLExecuteScalar(ConnectionString, "SELECT sum(productPrice) FROM cartTbl")
End Sub

Public Shared Function SQLExecuteScalar(ByVal ConnectionString As String, ByVal Query As String) As String
    Dim Result As String = Nothing

    Dim Exc As Exception = Nothing

    Using Conn As New SqlClient.SqlConnection(ConnectionString)
        Try
            'Open the connection
            Conn.Open()

            'Create the SQLCommand
            Using Cmd As New SqlClient.SqlCommand(Query, Conn)
                'Create an Object to receive the result
                Dim Obj As Object = Cmd.ExecuteScalar

                If (Obj IsNot Nothing) AndAlso (Obj IsNot DBNull.Value) Then
                    'If Obj is not NULL
                    Result = Obj.ToString
                End If
            End Using

        Catch ex As Exception
            'Save error so we can (if needed) close the connection
            Exc = ex

        Finally
            'Check if connection is closed
            If Not Conn.State = ConnectionState.Closed Then
                Conn.Close()
            End If

        End Try

    End Using

    'Check if any errors where found
    If Exc IsNot Nothing Then
        Throw Exc
    End If

    Return Result
End Function

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要扩展已经说过的内容，您可以使用以下方法使其更加灵活：

Private Sub Test()
    'Get/set connection string
    Me.TextBox1.Text = Me.SQLExecuteScalar(ConnectionString, "SELECT sum(productPrice) FROM cartTbl")
End Sub

Public Shared Function SQLExecuteScalar(ByVal ConnectionString As String, ByVal Query As String) As String
    Dim Result As String = Nothing

    Dim Exc As Exception = Nothing

    Using Conn As New SqlClient.SqlConnection(ConnectionString)
        Try
            'Open the connection
            Conn.Open()

            'Create the SQLCommand
            Using Cmd As New SqlClient.SqlCommand(Query, Conn)
                'Create an Object to receive the result
                Dim Obj As Object = Cmd.ExecuteScalar

                If (Obj IsNot Nothing) AndAlso (Obj IsNot DBNull.Value) Then
                    'If Obj is not NULL
                    Result = Obj.ToString
                End If
            End Using

        Catch ex As Exception
            'Save error so we can (if needed) close the connection
            Exc = ex

        Finally
            'Check if connection is closed
            If Not Conn.State = ConnectionState.Closed Then
                Conn.Close()
            End If

        End Try

    End Using

    'Check if any errors where found
    If Exc IsNot Nothing Then
        Throw Exc
    End If

    Return Result
End Function

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