MySQL database trigger

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