SQLite Forum

thank for your reply, I manage to change the subquery inside the update statement ,

```
CREATE TRIGGER updater
         AFTER UPDATE
            ON Rental
      FOR EACH ROW
          WHEN OLD.rental_cost IS NULL AND 
               NEW.date_back IS NOT NULL
BEGIN
    UPDATE Rental
       SET rental_cost = 3 + (
                                 SELECT price
                                   FROM Rental
                                        JOIN
                                        License USING (
                                            license_id
                                        )
                                        JOIN
                                        Title USING (
                                            title
                                        )
                             )
*                            0.05 * (date_out) - (date_back) 
     WHERE rental_cost = NULL;
END;

```

however, the new problem is the trigger not detecting the UPDATE statement and not fire. I believe is something wrong with my WHEN statement