MySqlDataReader: DataTable.Fill(reader) throws ConstraintException

Question

I have two tables orders and orderdetails

table orders (PK = id, UNIQUE index on orderno)

|id|orderno|
| 1|1000   |
| 2|1001   |

table orderdetails (PK = id)

|id|orderid|item|qty|
| 1|      1|ABC |  3|
| 2|      1|XYZ |  4|

Now I want to query the data with:

SELECT o.orderno, od.item, od.qty
  FROM orders o

INNER JOIN orderdetails od ON o.orderno = od.order

which returns:

|orderno|item|qty|
|1000   |ABC |  3|
|1000   |XYZ |  4|

However If I use the following code to load the result into a DataTable it fails:

var connectionString = "Server=localhost;Database=orders;Uid=root;";
var commandText = "SELECT o.orderno, od.item, od.qty" + Environment.NewLine +
                  "FROM orders o" + Environment.NewLine +
                  "INNER JOIN orderdetails od ON o.orderno = od.order";

var reader = MySqlHelper.ExecuteReader(connectionString, commandText);
var table = new DataTable("OrdersQuery");
table.Fill(reader); // throws ConstraintException

The problem is, that

table.Constraints[0]

is a UniqueConstraints on the orderno column. Propably because

reader.GetSchemaTable() 

has a IsUnique=true entry for orderno (which is true in the base table, but not true for the join query).

Even worse, that doesn't help either:

table.BeginLoadData(); // msdn docs claim that this should disable constraints
table.Load(reader);
table.EndLoadData();

Any ideas how to fix this?

StackTrace:

System.Data.ConstraintException Was Unhandled.
  Message=Failed to enable constraints. One or more rows contain values violating non-null, unique, or foreign-key constraints.
  Source=System.Data
  StackTrace:
       bei System.Data.DataTable.EnableConstraints()
       bei System.Data.DataTable.set_EnforceConstraints(Boolean value)
       bei System.Data.DataTable.EndLoadData()
       bei System.Data.Common.DataAdapter.FillFromReader(DataSet dataset, DataTable datatable, String srcTable, DataReaderContainer dataReader, Int32 startRecord, Int32 maxRecords, DataColumn parentChapterColumn, Object parentChapterValue)
       bei System.Data.Common.DataAdapter.Fill(DataTable[] dataTables, IDataReader dataReader, Int32 startRecord, Int32 maxRecords)
       bei System.Data.Common.LoadAdapter.FillFromReader(DataTable[] dataTables, IDataReader dataReader, Int32 startRecord, Int32 maxRecords)
       bei System.Data.DataTable.Load(IDataReader reader, LoadOption loadOption, FillErrorEventHandler errorHandler)
       bei System.Data.DataTable.Load(IDataReader reader)

Answer 1

I had the same problem but got it fixed by using the workaround from this post: http://bugs.mysql.com/bug.php?id=65065 (at bottom):

cmd.CommandText = "SELECT cam.no_serie, t.mnt FROM trx t LEFT JOIN camn cam USING(id_camn) ";
    MySqlDataReader dr = cmd.ExecuteReader();
    DataSet ds = new DataSet();
    DataTable dataTable = new DataTable();
    ds.Tables.Add(dataTable);
    ds.EnforceConstraints = false;
    dataTable.Load(dr);
    dr.Close();