Database cascading operation

Cascade operation

• Definition ： When modifying and deleting the primary key of the primary table , At the same time, update or delete the foreign key value from the table
• Cascade operation

1. Simultaneous updating

ALTER TABLE  Table name  ADD CONSTRAINT  Foreign key name 
	FOREIGN KEY ( Foreign key field name ) REFERENCES  Main table name ( Main table column name ) 
		ON UPDATE CASCADE

2. At the same time to delete

ALTER TABLE  Table name  ADD CONSTRAINT  Foreign key name 
	FOREIGN KEY ( Foreign key field name ) REFERENCES  Main table name ( Main table column name ) 
		ON DELETE CASCADE

3. Both update and delete

ALTER TABLE  Table name  ADD CONSTRAINT  Foreign key name 
	FOREIGN KEY ( Foreign key field name ) REFERENCES  Main table name ( Main table column name ) 
		ON UPDATE CASCADE
		ON DELETE CASCADE