Trigger problems

I have a problem with getting this trigger to compile. It involves a book database, with four tables. customer, book, supplier and telephone_purchase. The trigger is meant to increment the number of sales of a book whenever it is purchased but whatever i do i just can't get it to work.


CREATE OR REPLACE TRIGGER increase_book_total_no_sold
BEFORE DELETE or INSERT or UPDATE
ON book
FOR EACH ROW
BEGIN
if UPDATING then
UPDATE book
SET total_no_sold = :new.total_no_sold
WHERE book_isbn = ld.book_isbn;
end if;
if DELETING then
DELETE FROM book
WHERE book_isbn = ld.book_isbn;
end if;
if INSERTING then
INSERT INTO book
VALUES ( :new.book_isbn
,:new.total_no_sold

);
end if;
end;

hope someone can help me

it's likely that the table book has more than two columns so you need to provide values for all columns or change your insert statement to:

INSERT INTO book (book_isbn,total_no_sold)
VALUES ( :new.book_isbn
,:new.total_no_sold

thanks, but how do i test if the trigger works. It compiles ok but how do i test it?

By playing (insert,delete,update) with BOOK table.