MySQL Creating tables with Foreign Keys giving errno: 150

Question

I am trying to create a table in MySQL with two foreign keys, which reference the primary keys in 2 other tables, but I am getting an errno: 150 error and it will not create

Answer 1

I've found another reason this fails... case sensitive table names.

For this table definition

CREATE TABLE user (
  userId int PRIMARY KEY AUTO_INCREMENT,
  username varchar(30) NOT NULL
) ENGINE=InnoDB;

This table definition works

CREATE TABLE product (
  id int PRIMARY KEY AUTO_INCREMENT,
  userId int,
  FOREIGN KEY fkProductUser1(userId) REFERENCES **u**ser(userId)
) ENGINE=InnoDB;

whereas this one fails

CREATE TABLE product (
  id int PRIMARY KEY AUTO_INCREMENT,
  userId int,
  FOREIGN KEY fkProductUser1(userId) REFERENCES User(userId)
) ENGINE=InnoDB;

The fact that it worked on Windows and failed on Unix took me a couple of hours to figure out. Hope that helps someone else.