Update QueryException.php

lib/Doctrine/DBAL/Query/QueryException.php

@@ -38,4 +38,17 @@ class QueryException extends DBALException
             "any FROM or JOIN clause table. The currently registered " .
             "aliases are: " . implode(", ", $registeredAliases) . ".");
     }
+    
+    /**
+     * @param string $alias
+     * @param array  $registeredAliases
+     *
+     * @return \Doctrine\DBAL\Query\QueryException
+     */
+    static public function notUniqueAlias($alias, $registeredAliases)
+    {
+        return new self("The given alias '" . $alias . "' is not unique " .
+            "in FROM and JOIN clause table. The currently registered " .
+            "aliases are: " . implode(", ", $registeredAliases) . ".");
+    }
 }