如果我们销毁与其关联的表，触发器也会被销毁。这称为触发器的显式销毁。可以通过一个例子来理解 -
示例
假设我们在名为“Sample”的表上有一个名为“trigger_before_delete_sample”的触发器。现在，如果我们删除该表，那么与该表关联的上述触发器也将被删除。
mysql> Show Triggers\G
*************************** 1. row ***************************
Trigger: trigger_before_delete_sample
Event: DELETE
Table: sample
Statement: BEGIN
SET @count = if (@count IS NULL, 1, (@count+1));
INSERT INTO sample_rowaffected values (@count);
END
Timing: BEFORE
Created: 2017-11-21 12:31:58.70
sql_mode: ONLY_FULL_GROUP_BY,
STRICT_TRANS_TABLES,
NO_ZERO_IN_DATE,
NO_ZERO_DATE,
ERROR_FOR_DIVISION_BY_ZERO,
NO_AUTO_CREATE_USER,
NO_ENGINE_SUBSTITUTION
Definer: root@localhost
character_set_client: cp850
collation_connection: cp850_general_ci
Database Collation: latin1_swedish_ci
*************************** 2. row ***************************
Trigger: before_inser_studentage
Event: INSERT
Table: student_age
Statement: IF NEW.age < 0 THEN SET NEW.age = 0;
END IF
Timing: BEFORE
Created: 2017-11-21 11:26:15.34
sql_mode: ONLY_FULL_GROUP_BY,
STRICT_TRANS_TABLES,
NO_ZERO_IN_DATE,
NO_ZERO_DATE,
ERROR_FOR_DIVISION_BY_ZERO,
NO_AUTO_CREATE_USER,
NO_ENGINE_SUBSTITUTION
Definer: root@localhost
character_set_client: cp850
collation_connection: cp850_general_ci
Database Collation: latin1_swedish_ci
2 rows in set (0.01 sec)上面的结果集显示数据库中有两个触发器，其中一个触发器与名为“Sample”的表关联。现在，借助以下语句，我们将删除该表 -
mysql> DROP table sample;
Query OK, 0 rows affected (0.26 sec)现在借助以下语句，我们可以看到与名为“Sample”的表关联的触发器也被销毁了。
mysql> Show Triggers\G
*************************** 1. row ***************************
Trigger: before_inser_studentage
Event: INSERT
Table: student_age
Statement: IF NEW.age < 0 THEN SET NEW.age = 0;
END IF
Timing: BEFORE
Created: 2017-11-21 11:26:15.34
sql_mode: ONLY_FULL_GROUP_BY,
STRICT_TRANS_TABLES,
NO_ZERO_IN_DATE,
NO_ZERO_DATE,
ERROR_FOR_DIVISION_BY_ZERO,
NO_AUTO_CREATE_USER,
NO_ENGINE_SUBSTITUTION
Definer: root@localhost
character_set_client: cp850
collation_connection: cp850_general_ci
Database Collation: latin1_swedish_ci
1 row in set (0.01 sec)
