Integrity constraint violation: 1452 Cannot add or update a child row:

Question

I am trying to insert values into my comments table and I am getting a error. Its saying that I can not add or update child row and I have no idea what that means.

my schema looks something like this

-- ---------------------------- -- Table structure for `comments` -- ---------------------------- DROP TABLE IF EXISTS `comments`; CREATE TABLE `comments` (   `id` varchar(36) NOT NULL,   `project_id` varchar(36) NOT NULL,   `user_id` varchar(36) NOT NULL,   `task_id` varchar(36) NOT NULL,   `data_type_id` varchar(36) NOT NULL,   `data_path` varchar(255) DEFAULT NULL,   `message` longtext,   `created` datetime DEFAULT NULL,   `modified` datetime DEFAULT NULL,   PRIMARY KEY (`id`),   KEY `fk_comments_users` (`user_id`),   KEY `fk_comments_projects1` (`project_id`),   KEY `fk_comments_data_types1` (`data_type_id`),   CONSTRAINT `fk_comments_data_types1` FOREIGN KEY (`data_type_id`) REFERENCES `data_types` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,   CONSTRAINT `fk_comments_projects1` FOREIGN KEY (`project_id`) REFERENCES `projects` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,   CONSTRAINT `fk_comments_users` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION ) ENGINE=InnoDB DEFAULT CHARSET=utf32;  -- ---------------------------- -- Records of comments -- ----------------------------  -- ---------------------------- -- Table structure for `projects` -- ---------------------------- DROP TABLE IF EXISTS `projects`; CREATE TABLE `projects` (   `id` varchar(36) NOT NULL,   `user_id` varchar(36) NOT NULL,   `title` varchar(45) DEFAULT NULL,   `description` longtext,   `created` datetime DEFAULT NULL,   `modified` datetime DEFAULT NULL,   PRIMARY KEY (`id`),   KEY `fk_projects_users1` (`user_id`),   CONSTRAINT `fk_projects_users1` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION ) ENGINE=InnoDB DEFAULT CHARSET=utf32;  -- ---------------------------- -- Records of projects -- ---------------------------- INSERT INTO `projects` VALUES ('50dcbc72-3410-4596-8b71-0e80ae7aaee3', '50dcbc5c-d684-40bf-9715-0becae7aaee3', 'Brand New Project', 'This is a brand new project', '2012-12-27 15:24:02', '2012-12-27 15:24:02'); 

and the mysql statement I am trying to do looks something like this

INSERT INTO `anthonyl_fbpj`.`comments` (`project_id`, `user_id`, `task_id`, `data_type_id`, `message`, `modified`, `created`, `id`)  VALUES ('50dc845a-83e4-4db3-8705-5432ae7aaee3', '50dcbc5c-d684-40bf-9715-0becae7aaee3', '1', '50d32e5c-abdc-491a-a0ef-25d84e9f49a8', 'this is a test', '2012-12-27 19:20:46', '2012-12-27 19:20:46', '50dcf3ee-8bf4-4685-aa45-4eb4ae7aaee3') 

the error I get looks like this

SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (anthonyl_fbpj.comments, CONSTRAINT fk_comments_projects1 FOREIGN KEY (project_id) REFERENCES projects (id) ON DELETE NO ACTION ON UPDATE NO ACTION)

Answer 1

It just simply means that the value for column project_id on table comments you are inserting doesn't exist on table projects. Bear in mind that the values of column project_id on table comments is dependent on the values of ID on table Projects.

The value 50dc845a-83e4-4db3-8705-5432ae7aaee3 you are inserting for column project_id does not exist on table projects.

Answer 2

Make sure you have project_id in the fillable property of your Comment model.

I had the same issue, And this was the reason.