Using Triggers

MySQL statements are executed when needed, as are stored procedures. But what if you wanted a statement (or statements) to be executed automatically when events occur? For example: Every time a customer is added to a database table, check that the phone number is formatted correctly and that the state abbreviation is in uppercase, Every time a product is ordered, subtract the ordered quantity from the number in stock, Whenever a row is deleted, save a copy in an archive table.