To create a new trigger, use the CREATE TRIGGER
statement. You must give the trigger a unique name and then provide the timing,
action, and table that will cause the trigger to fire. For example, to create a
trigger that will fire every time a row is deleted from the products table, you
would construct a trigger as follows:
CREATE TRIGGER trigger_name BEFORE DELETE ON products FOR EACH ROW BEGIN ... END
The timing for a trigger can be BEFORE or
AFTER, indicating whether the trigger code should be executed
immediately before or immediately after the SQL statement that causes the
trigger to fire.
The keywords FOR EACH ROW are part of the CREATE
TRIGGER syntax and are required in every trigger.