bdd.query("DELETE FROM `questions` WHERE `id` = ? AND `owner` = ?",[questionID,user.id],function(err,res){
if(err)
callback(err,null)
else{
bdd.query("UPDATE `questions` SET `indexSet`=indexSet-1 WHERE `indexSet`>? AND `class`=? AND `owner`=?",[question.indexSet,question.class,user.id],callback);