diff --git a/dblayeroo.php b/dblayeroo.php
index b813239..5e08d1f 100644
--- a/dblayeroo.php
+++ b/dblayeroo.php
@@ -320,10 +320,10 @@ class dblayeroo
   {
     $this->debugLog ("Entering createTable");
     if ($this->sep === "")
-      throw new Exception (dgettext("domframework", "Database not connected"),
+      $this->DBException (dgettext("domframework", "Database not connected"),
                            500);
     if (count ($this->fields) === 0)
-      throw new Exception (dgettext("domframework", "No Field defined"), 500);
+      $this->DBException (dgettext("domframework", "No Field defined"), 500);
     if ($this->table === null)
       throw new \Exception (dgettext("domframework",
                             "No table name defined to create the table"), 500);
@@ -360,7 +360,7 @@ class dblayeroo
           $params  = array_slice ($params, 1);
           break;
         default:
-          throw new Exception (sprintf (
+          $this->DBException (sprintf (
                                dgettext("domframework",
                                "Unknown type '%s' provided for field '%s'"),
                                $this->fieldTypeLight ($field), $field), 500);
@@ -386,7 +386,7 @@ class dblayeroo
             $sql .= " AUTOINCREMENT";
             break;
           default:
-            throw new Exception (sprintf (dgettext("domframework",
+            $this->DBException (sprintf (dgettext("domframework",
                            "Unknown additionnal parameter '%s' for field '%s'"),
                            $p, $field), 500);
           }
@@ -397,7 +397,7 @@ class dblayeroo
       if ($this->unique !== null)
       {
         if (!is_array ($this->unique))
-          throw new Exception (dgettext("domframework",
+          $this->DBException (dgettext("domframework",
                                "The Unique field definition is not an array"),
                                500);
         foreach ($this->unique as $u)
@@ -458,7 +458,7 @@ class dblayeroo
           $params  = array_slice ($params, 1);
           break;
         default:
-          throw new Exception (sprintf (
+          $this->DBException (sprintf (
                                dgettext("domframework",
                                "Unknown type provided for field '%s'"),
                                $field), 500);
@@ -484,7 +484,7 @@ class dblayeroo
             $sql .= " AUTO_INCREMENT";
             break;
           default:
-            throw new Exception (sprintf (
+            $this->DBException (sprintf (
                                  dgettext("domframework",
                            "Unknown additionnal '%s' parameter for field '%s'"),
                            $p, $field), 500);
@@ -563,7 +563,7 @@ class dblayeroo
           $params  = array_slice ($params, 1);
           break;
           default:
-            throw new Exception (sprintf (
+            $this->DBException (sprintf (
                                  dgettext("domframework",
                                  "Unknown type provided for field '%s'"),
                                  $field), 500);
@@ -581,7 +581,7 @@ class dblayeroo
             {
             case "not null": $sql .= " NOT NULL"; break;
             default:
-              throw new Exception (sprintf (
+              $this->DBException (sprintf (
                                    dgettext("domframework",
                            "Unknown additionnal parameter '%s' for field '%s'"),
                            $p, $field), 500);
@@ -620,7 +620,7 @@ class dblayeroo
       $sql .=")";
       break;
     default:
-      throw new Exception (dgettext("domframework",
+      $this->DBException (dgettext("domframework",
                            "PDO Engine not supported in dbLayeroo"), 500);
     }
 
@@ -636,7 +636,7 @@ class dblayeroo
   {
     $this->debugLog ("Entering dropTable ()");
     if ($this->sep === "")
-      throw new Exception (dgettext("domframework", "Database not connected"));
+      $this->DBException (dgettext("domframework", "Database not connected"));
     if ($this->table === null)
       throw new \Exception (dgettext("domframework",
                             "No table name defined to drop the table"), 500);
@@ -907,7 +907,7 @@ class dblayeroo
                     "foreign" => $foreign);
       break;
     default:
-      throw new Exception (dgettext("domframework",
+      $this->DBException (dgettext("domframework",
         "PDO Engine not supported in dbLayeroo"), 500);
     }
   }
@@ -1576,6 +1576,7 @@ class dblayeroo
                                     "MIN","SUM")))
         {
           $aggregateFunction = true;
+echo "AGGRAGATE $this->table \n";
           // Aggregate function. Add the non aggregate fields to the GROUP BY
           // expression, if not already done
           if ($this->groupByExpression === null)
@@ -2124,7 +2125,6 @@ class dblayeroo
           $groupBy = array_merge ($groupBy, $ext);
         }
       }
-
     }
     // If there is some GROUP BY in join Object, but not in this object, all
     // the displayed fields must be added to be added in the GROUP BY
@@ -2134,6 +2134,22 @@ class dblayeroo
            empty ($this->groupByExpression))
        ))
       $this->groupByExpression = $this->displayColumn;
+    // If the local groupByExpression is set, but the external object was null,
+    // request the displayed fields to external objects
+    if (is_array ($this->groupByExpression) && $groupBy === null &&
+        $this->joinObject)
+    {
+      foreach ($this->joinObject as $obj)
+      {
+        $ext = $obj->displayGet (true);
+        if ($ext !== null)
+        {
+          if (! is_array ($groupBy))
+            $groupBy = array ();
+          $groupBy = array_merge ($groupBy, $ext);
+        }
+      }
+    }
     if (is_array ($this->groupByExpression))
     {
       if (! is_array ($groupBy))