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….