MySQL Database learning eight triggers operation

8.1 Triggers

When a table changes, some processing occurs automatically. For example, when each additional student record is added to the student table, the total number of students must be changed at the same time, and the phone number should be checked for correct format and address abbreviation.

　　The following statement activates the trigger:

• Delete statement.
• Insert statement.
• UPDATE statement.

MySQL 5 starts supporting trigger database objects.

8.2 Creating a Trigger

CREATE TRIGGER trigger_name    before| After trigger_event on table_name for each         ROW trigger_stmt;

Trigger_name: Trigger name.

Trigger_event:delete, insert, and update.

TABLE_NAME: The table that triggered the event.

TRIGGER_STMT: The statement executed after the trigger is activated.

To create a trigger that contains multiple execution statements

DELIMITER $$//set End symbol to $ $CREATE TRIGGER trigger_name    before| After trigger_event on         table_name for each ROW            BEGIN            trigger_stmt//Multiple execution statements, separated by            END            $ $DELIMITER ;//restore the end symbol setting to;

8.3 Viewing triggers

Trigger, Event, Table, Statement, Timing

SHOW TRIGGERS \g

Use INFORMATION_SCHEMA; SELECT * FROM triggers "WHERE trigger_name= ' trigger_name '" \g

8.4 Deleting a Trigger

DROP TRIGGER trigger_name;

　　

MySQL Database learning eight triggers operation