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
was added in MySQL 5.0.2. Its use 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 12.4.5.41, “SHOW WARNINGS Syntax”.
Triggers for a table are also dropped if you drop the table.
When upgrading from a version of MySQL older than MySQL 5.0.10
to 5.0.10 or newer—including all MySQL 5.5
releases—you must drop all triggers before
upgrading and re-create them afterward, or else
DROP TRIGGER does not work after
the upgrade.