MySQL 5.7 Release Notes
DROP TRIGGER [IF EXISTS] [schema_name.]trigger_name
This statement drops a trigger. The schema (database) name is
optional. If the schema is omitted, the trigger is dropped from
the default schema. DROP TRIGGER
requires the TRIGGER privilege for
the table associated with the trigger.
Use IF EXISTS to prevent an error from
occurring for a trigger that does not exist. A
NOTE is generated for a nonexistent trigger
when using IF EXISTS. See
Section 13.7.5.40, “SHOW WARNINGS Statement”.
Triggers for a table are also dropped if you drop the table.