Question

I am having trouble creating a table with MySQL. I have narrowed the problem down to the enrolled table.
The error I get is: #1005 – Can’t create table ‘mcems.enrolled’ (errno: 150)
http://pastebin.com/9cUkgs8p

Answer 1

CRN field should be the same type in both tables, MCEMS.courses and MCEMS.enrolled; otherwise, you cannot use it in FOREIGN KEY. You have

CREATE  TABLE IF NOT EXISTS `MCEMS`.`courses` (
`CRN` INT NOT NULL , ...)  
and 
CREATE  TABLE IF NOT EXISTS `MCEMS`.`enrolled` (  
`user_id` INT NOT NULL ,    
`CRN` VARCHAR(45) , -- must be INT (also NOT NULL because it's part of PK)!!!
PRIMARY KEY (`user_id`, `CRN`) ,
INDEX `user_id` (`user_id` ASC) ,
INDEX `CRN` (`CRN` ASC) ,
FOREIGN KEY (`user_id`)
REFERENCES `MCEMS`.`users` (`user_id`)
ON DELETE CASCADE
ON UPDATE CASCADE,
FOREIGN KEY (`CRN`)
REFERENCES `MCEMS`.`courses` (`CRN`)
ON DELETE CASCADE
ON UPDATE CASCADE)

Also, absolutely no need for INDEX user_id (user_id ASC)