删除重复数据少加一个天数导致误删数据

$user_sign_obj = new Data_Other_ShopusersignModel();


 $_sql = "select lender_id,sign_day from shop_user_sign group by lender_id,sign_day having count(*) > 1";
 $list = $user_sign_obj->Fetch($_sql);


 foreach ($list as $key => $val) {
         echo 'lender_id:', $val['lender_id'], PHP_EOL;
         $_sql = "select * from shop_user_sign  where lender_id={$val['lender_id']} and sign_day='{$val['sign_day']}'";
         $sign_list = $user_sign_obj->Fetch($_sql);
          foreach ($sign_list as $k=>$value) {
             $id = $sign_list[0]['id'];
             $delete_sql = "delete from shop_user_sign where id != {$id} and lender_id={$val['lender_id']} and sign_day='{$val['sign_day']}'";
             $user_sign_obj->Fetch($delete_sql);a
         }   
 }