在VB.net中用SQL查询读取平均值

我需要在vb.net中运行SQL查询，以查找我的应用程序的平均评级。我认为这是正确的SQL：

SELECT AVG(Rating) FROM Feedback;

唯一的问题是我不知道如何正确运行这个查询。我有一个类似的问题，我已经改成了下面的（它不起作用），我只是想知道你是否可以帮助调整它，使它真正起作用

    Dim conn As New MySqlConnection(DBCred)
    Dim sqlquery As String = "SELECT AVG(Rating) FROM Feedback;"
    Dim cmd As MySqlCommand
    Dim AVGRating As String
    conn.Close()
    cmd = New MySqlCommand(sqlquery, conn)
    conn.Open()
    Try
        AVGRating = cmd.r
    Finally
        cmd.Connection.Close()

    End Try
    conn.Close()

谢谢

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Chris

您需要执行命令-在本例中，使用

ExecuteScalar

AVGRating = cmd.ExecuteScalar().ToString()

试试这个

    Dim AVGRating As String = String.Empty
    Using xConn As New MySqlConnection(DBCred)
        Using xComm As New MySqlCommand()
            With xComm
                .Connection = xConn
                .CommandType = CommandType.Text
                .CommandText = "SELECT AVG(Rating) FROM Feedback WHERE Feedback.Rating > 0"
            End With
            Try
                xConn.Open()
                AVGRating = CStr(xComm.ExecuteScalar)
            Catch ex As Exception
                MsgBox(ex.Message.ToString)
            Finally
                xConn.Close()
            End Try
        End Using
    End Using

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如果我没记错，您可能需要添加一个别名：

选择平均（评级）作为评级…