Dependant Courses example sql db

varsity.sql

CREATE SCHEMA IF NOT EXISTS `varsity`;

CREATE TABLE `varsity`.`courses` (
  `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
  `name` VARCHAR(45) NULL,
  PRIMARY KEY (`id`));
  
CREATE TABLE `varsity`.`prerequisites` (
  `parent_course_id` BIGINT UNSIGNED NOT NULL,
  `child_course_id` BIGINT UNSIGNED NOT NULL,
  PRIMARY KEY (`parent_course_id`, `child_course_id`),
  FOREIGN KEY (`parent_course_id`) REFERENCES courses(`id`),
  FOREIGN KEY (`child_course_id`) REFERENCES courses(`id`),
  UNIQUE `unique_index`(`parent_course_id`, `child_course_id`)
  );
  
  
 INSERT INTO `varsity`.`courses` (`name`) VALUES 
 ("John's Intro to SQL"),
 ("John's Secondary SQL Course"), 
 ("John's MySQL Course"), 
 ("John's Advanced MySQL Course");
 
 INSERT INTO `varsity`.`prerequisites` (`parent_course_id`, `child_course_id`) VALUES
 (2, 1),
 (3, 1),
 (4, 1),
 (4, 2),
 (4, 3)