MySQL database trigger
1. Trigger with only one row of statements executed
Trigger triggers are events that trigger certain operations, such as insert, delete, and update.
For example:
Create trigger t_user_trig before insert
On t_user for each row
Insert into trigger_time values (now ());
Create a trigger named t_user_trig to insert the current time to the trigger_time table when inserting the t_user table.
Test:
Insert into t_user values (2, 'wang ', 0, 'abcdef', now (), 'A ');
Select * from trigger_time;
2. Trigger with multi-row statement execution
Example:
Delimiter &&
Create trigger t_user_trig_del after delete
On t_user for each row
Begin
Insert into trigger_time values ('2017-01-01 10:10:00 ');
Insert into trigger_time values ('2017-01-01 11:11:00 ');
End
&&
Delimiter;
Create a trigger named t_user_trig_del. After deleting the t_user record in the table, two insert statements are executed.
Select * from trigger_time;
3. View triggers
Select * from information_schema.triggers where trigger_name = 't_user_trig ';
4. delete a trigger