捕获重复的条目OleDbException＆覆盖

Question

尝试向Access数据库中添加行时，在处理条目时出现此错误。问题是我正在处理的某些条目是唯一的，有些可能具有重复的主键，并且具有对相关列的更新。但是，由于某些密钥具有重复的主键，因此所有处理都将失败。

我想用新数据覆盖重复的条目并添加新的条目。我该怎么做？

我在下面做了一些测试，以尝试使用try / catch块解决所有未能解决的问题，但无济于事：

            using (OleDbConnection myCon = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\\Users\\Lenovo\\Desktop\\Weather Cruncher\\wcMainDB.accdb"))
            {
                OleDbCommand cmd = new OleDbCommand();
                cmd.CommandText = "Insert into stations_NOAA " +
                    "([stationID],[stationName],[stationMinDate],[stationMaxDate],[stationDataCoverage]," +
                    "[stationLatitude],[stationLongitude],[stationElevation],[stationElevationUnit])" +
                    "values (?,?,?,?,?,?,?,?,?)";
                cmd.Connection = myCon;
                myCon.Open();

                // Populate Access Database
                foreach (Station loc in noaa.results)
                {
                    try
                    {
                        cmd.Parameters.AddWithValue("@stationID", loc.id); // Short Text data type
                        cmd.Parameters.AddWithValue("@stationName", loc.name); // Short Text data type
                        cmd.Parameters.AddWithValue("@stationMinDate", loc.mindate); // Short Text data type
                        cmd.Parameters.AddWithValue("@stationMaxDate", loc.maxdate); // Short Text data type
                        cmd.Parameters.AddWithValue("@stationDataCoverage", loc.datacoverage); // Number data type
                        cmd.Parameters.AddWithValue("@stationLatitude", loc.latitude); // Number data type
                        cmd.Parameters.AddWithValue("@stationLongitude", loc.longitude); // Number data type
                        cmd.Parameters.AddWithValue("@stationElevation", loc.elevation); // Number data type
                        cmd.Parameters.AddWithValue("@stationElevationUnit", loc.elevationUnit); // Short Text data type
                        cmd.ExecuteNonQuery();
                        cmd.Parameters.Clear();
                    }
                    catch(Exception ex)
                    {
                        if (ex.Message.Contains("duplicate values")) // It is a primary key violation, ignore
                        {
                            Console.WriteLine("Dupe skipped.");
                            continue;
                        }
                        else
                        {
                            MessageBox.Show(ex.ToString() + "\n\n" + ex.Message);
                        }
                    }
                }
            }

它正在处理20个查询，其中15个是唯一的。在将主键与程序正在处理的数据进行比较时，我观察了它的过程。如何解决这两个问题？

Answer 1

也许考虑这样的事情...假设Station_ID是唯一字段...

foreach (Station loc in noaa.results)
{
    cmdCount.CommandText = "SELECT count(*) from stations_NOAA WHERE StationId = @station_id";
    cmdCount.Parameters.AddWithValue("@station_id", loc.id);
    int count = (int)cmdCount.ExecuteScalar();

    if (count > 0)
    {
         // UPDATE STATEMENT
         cmd.CommandText "UPDATE stations_NOAA Set stationMinDate = @stationMinDate, Set StationMaxDate = @stationMaxDate, ...
             where StationID = @stationID;"
        cmd.Parameters.AddWithValue("@stationID", loc.id); // Short Text data type
        cmd.Parameters.AddWithValue("@stationMinDate", loc.mindate); // Short Text data type
        cmd.Parameters.AddWithValue("@stationMaxDate", loc.maxdate); // Short Text data type
        ...
        ...
        cmd.ExecuteNonQuery();
    }
    else
    {
         // INSERT STATEMENT
         commandText = ("Insert into stations_NOAA " +
                        "([stationID],[stationName],[stationMinDate],[stationMaxDate],[stationDataCoverage]," +
                        "[stationLatitude],[stationLongitude],[stationElevation],[stationElevationUnit])" +
                        "values (?,?,?,?,?,?,?,?,?)";
         cmd.Parameters.AddWithValue("@stationID", loc.id); // Short Text data type
        cmd.Parameters.AddWithValue("@stationMinDate", loc.mindate); // Short Text data type
        cmd.Parameters.AddWithValue("@stationMaxDate", loc.maxdate); // Short Text data type
        ...
        ...
        cmd.ExecuteNonQuery();
    }
    cmd.Parameters.Clear();
}

如果更新和插入中的所有参数都相同，则此模式：

foreach (Station loc in noaa.results)
{
    cmd.CommandText = "SELECT count(*) from stations_NOAA WHERE StationId = @station_id", myConnection);
    cmdCount.Parameters.AddWithValue("@station_id", loc.id);
    int count = (int)cmdCount.ExecuteScalar();

    if (count > 0)
        cmd.CommandText "UPDATE stations_NOAA " _
            "Set stationMinDate = @stationMinDate, " _
            "Set StationMaxDate = @ StationMaxDate, " _
               ...
            "where StationID = @stationID;"

    else
        commandText = "Insert into stations_NOAA " +
                        "([stationID],[stationName],[stationMinDate],[stationMaxDate],[stationDataCoverage]," +
                        "[stationLatitude],[stationLongitude],[stationElevation],[stationElevationUnit])" +
                        "values (@stationID,@stationMinDate, @ ...)";

    cmd.Parameters.AddWithValue("@stationID", loc.id); // Short Text data type
    cmd.Parameters.AddWithValue("@stationMinDate", loc.mindate); // Short Text data type
    cmd.Parameters.AddWithValue("@stationMaxDate", loc.maxdate); // Short Text data type
    ...
    ...

    cmd.ExecuteNonQuery();      

    cmd.Parameters.Clear();
}

但是仅当Insert和Update具有相同的字段并且更容易阅读时，这才有效。