Write rating for a user and an object. 
        {
                global $ilDB;
                if ($a_user_id == ANONYMOUS_USER_ID)
                {
                        return;
                }
                
                if($a_category_id)
                {
                        $ilDB->manipulate("DELETE FROM il_rating WHERE ".
                                "user_id = ".$ilDB->quote($a_user_id, "integer")." AND ".
                                "obj_id = ".$ilDB->quote((int) $a_obj_id, "integer")." AND ".
                                "obj_type = ".$ilDB->quote($a_obj_type, "text")." AND ".
                                "sub_obj_id = ".$ilDB->quote((int) $a_sub_obj_id, "integer")." AND ".
                                $ilDB->equals("sub_obj_type", $a_sub_obj_type, "text", true)." AND ".
                                "category_id = ".$ilDB->quote(0, "integer"));
                }
                
                $ilDB->manipulate("DELETE FROM il_rating WHERE ".
                        "user_id = ".$ilDB->quote($a_user_id, "integer")." AND ".
                        "obj_id = ".$ilDB->quote((int) $a_obj_id, "integer")." AND ".
                        "obj_type = ".$ilDB->quote($a_obj_type, "text")." AND ".
                        "sub_obj_id = ".$ilDB->quote((int) $a_sub_obj_id, "integer")." AND ".
                        $ilDB->equals("sub_obj_type", $a_sub_obj_type, "text", true)." AND ".
                        "category_id = ".$ilDB->quote((int) $a_category_id, "integer"));
                
                $ilDB->manipulate("INSERT INTO il_rating (user_id, obj_id, obj_type,".
                        "sub_obj_id, sub_obj_type, category_id, rating, tstamp) VALUES (".
                        $ilDB->quote($a_user_id, "integer").",".
                        $ilDB->quote((int) $a_obj_id, "integer").",".
                        $ilDB->quote($a_obj_type, "text").",".
                        $ilDB->quote((int) $a_sub_obj_id, "integer").",".
                        $ilDB->quote($a_sub_obj_type, "text").",".
                        $ilDB->quote($a_category_id, "integer").",".
                        $ilDB->quote((int) $a_rating, "integer").",".
                        $ilDB->quote(time(), "integer").")");
        }