sql - how to write a mysql trigger to log history -

i have never written trigger before , following tutorial http://net.tutsplus.com/tutorials/databases/introduction-to-mysql-triggers/ confused something.

i trying write trigger pulls data table after insert , logs in history table. here's code far:

delimiter $$  create trigger trackhistory after insert on test.inventory each row begin *** end;  delimiter ; 

i need add insert history... query, don't understand how reference fields on correct row of 'inventory' table. answer same , update or delete?

edit: have tried follow advice of answer below, didn't work got error

1363 - there no old row in on insert trigger. whats wrong?

delimiter $$  create trigger trackinserthistory after insert on inventory each row begin     insert history     values (new.id, old.quantity, new.quantity, timestamp); end$$  create trigger trackstockhistory after update on inventory each row begin     insert history     values (new.id, old.quantity, new.quantity, timestamp); end$$  delimiter ; 

they referenced new , old.

new new record inserted or updated data.

old deleted record, or old data before update.