MySQL : ERROR 1215 (HY000): Cannot add foreign key constraint

Question

I have read Database system concepts, 6th edition, Silberschatz. I\'m going to implement the university database system shown in chapter 2 on OS X

Answer 1

I had this error when I tried to import (in MysqlWorkbench) from a PhpAdminMySQL export. After verifying I had disabled the unique keys and foreign keys with:

SET unique_checks=0;
SET foreign_key_checks = 0;

I still get the same error (MySQL : ERROR 1215 (HY000): Cannot add foreign key constraint). The error occurred on this create statement.

DROP TABLE IF EXISTS `f1_pool`;
CREATE TABLE `f1_pool` (
 `id` int(11) NOT NULL,
 `name` varchar(45) NOT NULL,
 `description` varchar(45) DEFAULT NULL COMMENT 'Optional',
 `ownerId` int(11) NOT NULL,
 `lastmodified` timestamp NOT NULL DEFAULT current_timestamp() ON UPDATE current_timestamp()
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

No foreign key or unique index, so what is wrong here? Finally (after 90 minutes puzzling) I decided to restart MySQL and do the import again with one modification: I dropped all tables before doing the import. And there was no error, all functioned, tables and views restored. So my advice, if all looks ok, first try to restart MySQL!