Crystal Report multi table failure

I'm still new to C# and reports, and in order to take baby steps, I started with a Crystal Report using one table.

Eventually I figured it out and it worked brilliantly.

Then I added another table to the report. I haven't changed anything in my code. Adding a field from the second table to the report, results in a blank report.

Removing that field again (so no columns form the second table is on the report), the report produces data again.

So I get the impression that the problem is on the report side. But I have included the code anyway:

private void Load_Ord_Rep()
 {
     using (MySqlConnection conn = new MySqlConnection(OTW.Properties.Settings.Default.wcdbConnectionString))
     {
         conn.Open();
 
         String sql = "SELECT * FROM wcdb.order_table, wcdb.mat_table WHERE order_no = '13661' and order_table.mat_code = mat_table.mat_code";
 
         using (MySqlCommand cmdSel = new MySqlCommand(sql, conn))
         {
 
             DataSet ds = new DataSet();
             MySqlDataAdapter da = new MySqlDataAdapter(cmdSel);
 
             da.Fill(ds);
 
             ReportDocument rpt = new ReportDocument();
             rpt.Load("C:\\Visual Studio 2008\\Projects\\OTW\\OTW\\CrystalReport3.rpt");
 
             dataView1.Table = ds.Tables[0];
             rpt.SetDataSource(dataView1);
 
 
             crystalReportViewer1.ReportSource = rpt;
             crystalReportViewer1.Refresh();
         }
         conn.Close();
     } 
 }
 

With further investigation I have come to the conclusion the problem is not the code or the link, but rather the loading of the second table. I did a outer join with the values being equal or greater. Only the first table's results are displayed on the report. So because the second table's values are not read, no join can be established between the two tables and thus no data on the report. Now the question: why is the second table not being read by Crystal Report!?

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