Foreign Key Failure - mysql

Question

Ok, so I've been trying to figure out why I keep getting this specific error. MySql keeps giving me error code 1452. Cannot add or update a child row. My tables are as such.
CREATE TABLE IF NOT EXISTS `ecommerce`.`departments` (
`id` INT NOT NULL AUTO_INCREMENT ,
`name` VARCHAR(100) NOT NULL ,
PRIMARY KEY (`id`) )
ENGINE = MyISAM;
INSERT INTO `ecommerce`.`departments`
VALUES (1, 'Development'), (2, 'Marketing'),
(3, 'Sales'), (4, 'Customer Service');
CREATE TABLE IF NOT EXISTS `ecommerce`.`department_roles` (
`id` INT NOT NULL AUTO_INCREMENT ,
`name` VARCHAR(100) NOT NULL ,
`map` VARCHAR(255) NOT NULL ,
`parent_id` INT NOT NULL ,
PRIMARY KEY (`id`) )
ENGINE = MyISAM;
INSERT INTO `ecommerce`.`department_roles`
VALUES (1, 'Admin', '/admin', 0), (2, 'Create', '/admin', 1),
(3, 'Update', '/admin', 1), (4, 'Delete', '/admin', 1);
CREATE TABLE IF NOT EXISTS `ecommerce`.`department_roles_map` (
`id` INT NOT NULL AUTO_INCREMENT ,
`department_roles_id` INT NOT NULL ,
`departments_id` INT NOT NULL ,
PRIMARY KEY (`id`) ,
INDEX `fk_drm_departments` (`departments_id` ASC) ,
INDEX `fk_drm_department_roles` (`department_roles_id` ASC) ,
CONSTRAINT `fk_drm_departments`
FOREIGN KEY (`departments_id` )
REFERENCES `ecommerce`.`departments` (`id` )
ON DELETE CASCADE
ON UPDATE NO ACTION,
CONSTRAINT `fk_drm_department_roles`
FOREIGN KEY (`department_roles_id` )
REFERENCES `ecommerce`.`department_roles` (`id` )
ON DELETE CASCADE
ON UPDATE NO ACTION)
ENGINE = InnoDB;
Now, when I try to select from departments and department_roles, I show data.
SELECT * FROM department_roles;
+----+--------+--------+-----------+
| id | name | map | parent_id |
+----+--------+--------+-----------+
| 1 | Admin | /admin | 0 |
| 2 | Create | /admin | 1 |
| 3 | Update | /admin | 1 |
| 4 | Delete | /admin | 1 |
+----+--------+--------+-----------+
4 rows in set (0.00 sec)
SELECT * FROM departments;
+----+--------+--------+-----------+
| id | name | map | parent_id |
+----+--------+--------+-----------+
| 1 | Admin | /admin | 0 |
| 2 | Create | /admin | 1 |
| 3 | Update | /admin | 1 |
| 4 | Delete | /admin | 1 |
+----+--------+--------+-----------+
4 rows in set (0.00 sec)
But, when I try to insert into department_roles_map, I get this.
INSERT INTO department_roles_map(department_roles_id, departments_id) VALUES (1, 1);
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`ecommerce`.`department_roles_map`, CONSTRAINT `fk_drm_departments` FOREIGN KEY (`departments_id`) REFERENCES `departments` (`id`) ON DELETE CASCADE ON UPDATE NO ACTION)
Any help would be much appreciated!

Answer 1

Firstly, I'm impressed that you managed to create an InnoDB table that has FK references to two MyISAM tables!
Try creating all three table with InnoDB engine and trying again....

Answer 2

Both the parent and the child tables need to use the InnoDB storage engine, but you're using MyISAM for the parent tables.
My guess is that there is already a table named department_roles_map, so when you runCREATE TABLE IF NOT EXISTS it's failing because the table already exists, and ignoring the error. Then when you try to insert data into the other department_roles_map, it fails with the FK error.
But that's just a guess.
I agree with Tom Mac, try creating all 3 tables using InnoDB, but you should also confirm that no other tables with those names already exists.