Referential integrity in mysql

Referential integrity in mysql:
http://dev.mysql.com/tech-resources/articles/mysql-enforcing-foreign-keys.html
In student table:
student_id is primary key, teacher_id is foreign key
When we enter teacher_id in student table, we want to make sure  teacher_id exsits in teacher table,
There are difference for  InnoDB, NDB and MyISAM storage engines.
For InnoDB, we used

 FOREIGN KEY (teacher_id) REFERENCES teacher (teacher_id)

For MyISAM

 PRIMARY KEY (student_id, teacher_id)

 We may also Cascade UPDATES and DELETES in programming.