提取的固定值

Question

我有一個表在MySQL具有兩個柱日期和總數 .I想通過寫query.so其以提取關於當前日期的總數我可以使用預先

Private Sub Button1_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click 
    MysqlConn = New MySqlConnection 
    MysqlConn.ConnectionString = "Server = localhost; User Id = root; Password=;Database=project" 
    Dim Reader As MySqlDataReader 
    Try 
     MysqlConn.Open() 

     Dim todaysdate As String = String.Format("{0:yyyy-MM-dd}", DateTime.Now) 
     Dim Query As String 
     Query = "select * from project.total_number where date=DateTime.Now" 
     Command = New MySqlCommand(Query, MysqlConn) 
     Reader = Command.ExecuteReader 
     MessageBox.Show("data saved") 
     MysqlConn.Close() 

    Catch ex As MySqlException 
     MessageBox.Show(ex.Message) 
    Finally 
     MysqlConn.Dispose() 

    End Try 

我已經完成的工作，但Datetime.Now正顯示出error.i進一步calculation.thanks總數要使用在計算

Answer 1

您的查詢結果在您的中使用條件（where date=DateTime.Now），就好像它是一個字符串文字，這就是爲什麼錯誤您收到。將其更改爲以下

Query = "select * from project.total_number where `date`=" & DateTime.Now; 

（OR）更好地使用參數化查詢，以避免SQL注入像

Query = "select * from project.total_number where `date`= @dateval" 
Command = New MySqlCommand(Query, MysqlConn) 
With Command 
     .Parameters.AddWithValue("@dateval", DateTime.Now) 
End With