private MyCatSchemaCollection GetTable(string sql)
        {
            MyCatSchemaCollection c      = new MyCatSchemaCollection();
            MyCatCommand          cmd    = new MyCatCommand(sql, connection);
            MyCatDataReader       reader = cmd.ExecuteReader();

            // add columns
            for (int i = 0; i < reader.FieldCount; i++)
            {
                c.AddColumn(reader.GetName(i), reader.GetFieldType(i));
            }

            using (reader)
            {
                while (reader.Read())
                {
                    MyCatSchemaRow row = c.AddRow();
                    for (int i = 0; i < reader.FieldCount; i++)
                    {
                        row[i] = reader.GetValue(i);
                    }
                }
            }
            return(c);
        }