MySQL：INTERVAL问题

Question

我正在寻找一个星期的间隔，但6岁以下的任何东西都给了我：

 timeIn > DATE_SUB(NOW(), INTERVAL 1 WEEK)
Error:  Invalid attempt to Read when reader is closed.

 timeIn > DATE_SUB(NOW(), INTERVAL 6 WEEK)  //6 or anything above 6 and the query works
Error:  Invalid attempt to Read when reader is closed.

以下是我正在执行查询的方式（这有效，但是当我将INTERVAL从6更改为更少的东西时，我的读取器被关闭错误）：

        string sql = "SELECT rooms.building, rooms.room, " +
        "users.FirstName, users.LastName, users.adUname,  " +
        "ingressegresslogs.timeIn, ingressegresslogs.timeOut, rooms.Id  " +
        "FROM rooms, users, ingressegresslogs  " +
        "WHERE  ingressegresslogs.RoomId = rooms.Id  " +
        "AND ingressegresslogs.timeIn > DATE_SUB(NOW(), INTERVAL 6 WEEK) "
        "AND ingressegresslogs.UserId = users.id " +
        "ORDER BY rooms.Id ASC, ingressegresslogs.timeIn ASC";        

    MySqlCommand cmd = new MySqlCommand(sql, conn);

    MySqlDataReader rdr = cmd.ExecuteReader();

编辑：此查询的工作原理是mysql命令行和INTERVAL 1 WEEK，而不是C＃代码。返回带有数据的428行

这是读者代码，可能是问题所在。

MySqlCommand cmd = new MySqlCommand(sql, conn);

            MySqlDataReader rdr = cmd.ExecuteReader();

            if (!rdr.HasRows)
            {
                rdr.Close();
                // EventLog.WriteEntry("IEReporter", "Database returned nothing", EventLogEntryType.Error, 234);           
            }

            while (rdr.Read())
            {

                try
                {
                    IELog queryResult = new IELog();

                    queryResult.RoomID = rdr.GetString("Id");
                    queryResult.FirstName = rdr.GetString("FirstName");
                    queryResult.LastName = rdr.GetString("LastName");
                    queryResult.ADUname = rdr.GetString("ADUname");
                    queryResult.Building = rdr.GetString("Building");
                    queryResult.Room = rdr.GetString("room");
                    queryResult.Ingresstime = rdr.GetDateTime ("timeIn");
                    //  timeOut might be null
                    if (Convert.IsDBNull(rdr["timeOut"]))
                        {

                            queryResult.Egresstime = new DateTime(1111, 1, 11);
                        }
                    else
                        {
                            queryResult.Egresstime = rdr.GetDateTime("timeOut");
                        }

                    queryResultList.Add(queryResult);

                }
                catch (Exception ex)
                {
                    Console.WriteLine("LogDAO build list:  " + ex);
                }
            }
            // Count rows
            //Console.WriteLine("Row Count: {0}", queryResultList.Count);

            rdr.Close();
            return queryResultList;

Answer 1

SQL适用于我：

mysql> select DATE_SUB(NOW(), INTERVAL 1 WEEK);
+----------------------------------+
| DATE_SUB(NOW(), INTERVAL 1 WEEK) |
+----------------------------------+
| 2011-07-07 01:16:50              |
+----------------------------------+

你的问题是你没有返回任何行，这就是读者爆炸的原因吗？

Answer 2

查看您发布的代码，您可能希望在确定没有行后立即返回。

        if (!rdr.HasRows)
        {
            rdr.Close();
            // EventLog.WriteEntry("IEReporter", "Database returned nothing", EventLogEntryType.Error, 234);           
            return; // do this, or otherwise skip the read below
        }