ShowTriggers\G******************************1.row****************** ************ &"/> ShowTriggers\G******************************1.row****************** ************ &">
#If we destroy the table associated with it, the trigger will also be destroyed. This is called explicit destruction of the trigger. It can be understood through an example -
Suppose we have a trigger named "trigger_before_delete_sample" on a table named "Sample". Now, if we delete the table, then the above triggers associated with the table will also be deleted.
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)
The above result set shows that there are two triggers in the database, one of which is associated with the table named "Sample". Now, with the help of the following statement, we will delete the table -
mysql> DROP table sample; Query OK, 0 rows affected (0.26 sec)
Now with the help of the following statement, we can see that the triggers associated with the table named "Sample" are also destroyed.
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)
The above is the detailed content of What happens to the trigger when we delete the table that has that trigger?. For more information, please follow other related articles on the PHP Chinese website!