Cascade on delete sql [duplicate] - php

Question

This question already has answers here:
MySQL foreign key constraints, cascade delete
(3 answers)
Closed 8 years ago.
Im working on a small website that involves the use of databases, I'm using this two tables to users, in the first table i add the users and his information, and in the second one I add only the user id the course id.
My question is how can I add the cascade on delete, in which table?
CREATE TABLE IF NOT EXISTS `students` (
`studentid` int(11) NOT NULL AUTO_INCREMENT,
`fname` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`lname` varchar(64) COLLATE utf8_unicode_ci NOT NULL,
`studentcode` varchar(16) COLLATE utf8_unicode_ci NOT NULL,
`courseid` int(11) NOT NULL,
PRIMARY KEY (`studentid`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=27 ;
CREATE TABLE IF NOT EXISTS `idtables` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`courseid` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`studentid` char(64) COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=43 ;

Answer 1

You need to define this behaviour in a FOREIGN KEY constraint like:
CREATE TABLE IF NOT EXISTS `idtables` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`courseid` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`studentid` char(64) COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (`id`),
FOREIGN KEY fk_students_id (studentid)
REFERENCES students (id)
ON DELETE CASCADE
ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci AUTO_INCREMENT=43 ;

Answer 2

You need to create a FORIEGN KEY referencing to students table studentid with ON DELETE CASCADE option like below
CREATE TABLE IF NOT EXISTS `idtables` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`courseid` varchar(255) COLLATE utf8_unicode_ci NOT NULL,
`studentid` char(64) COLLATE utf8_unicode_ci NOT NULL,
PRIMARY KEY (`id`),
CONSTRAINT FK1 FORIEGN KEY(studentid) REFERENCES students(studentid) <-- Here
ON DELETE CASCADE <-- HERE
)