Fifth Chapter Trigger

Create a trigger

Grammar:

Create TRIGGER Trigger name before|after trigger event on table name for each row execution statement

Note: There can only be one trigger event at the same trigger time, such as the before of insert time can only have one departure event

Create a trigger_time table first:

Mysql> CREATE TABLE Trigger_time (Insert_time datetime);

Create a trigger that has only one execution statement

To create a trigger:

Mysql> CREATE trigger DEPT_TRIG1 before insert on Department for each row insert to Trigger_time values (now ());

In this way, when a record is inserted into the department table, the current time is inserted into the Trigger_time table.

to create a trigger with more than one execution statement

Grammar:

Create TRIGGER Trigger name before|after departure event on indicates for each row

Begin

Execute statement List

End

Note: MySQL defaults to ";" As the end. In the process of creating a trigger, you need to use ";" to solve this problem, you can use "delimiter &&" to change the Terminator to && After the trigger is created, use "delimiter;" Changes the Terminator to ";".

Mysql> delimiter &&

Mysql> CREATE trigger DEPT_TRIG2 after delete on department for each row

Begin

INSERT into Trigger_time values (now ());

INSERT into Trigger_time values (now ());

-End

&&

view triggers

Grammar:

Show triggers;

Delete Trigger

Grammar:

Drop trigger trigger name;

Fifth Chapter Trigger