MySQL #1452 - Cannot add or update a child row

Question

I'm begginer here, all what i'm trying to do is insert into a table field which is a foreign key, please take a look at this two tables :

Table Categorie

CREATE TABLE IF NOT EXISTS `categorie` (
    `id_cat` int(2) NOT NULL AUTO_INCREMENT,   
    `nom_cat` varchar(20) NOT NULL,   
    PRIMARY KEY (`id_cat`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1;

and table Annonce

CREATE TABLE IF NOT EXISTS `annonce` (
  `id_annonce` int(6) NOT NULL AUTO_INCREMENT,
  `titre` varchar(30) NOT NULL,
  `description` varchar(255) NOT NULL,
  `tarif` float NOT NULL,
  `deplacement` int(2) NOT NULL,
  `date_creation` date NOT NULL,
  `date_expiration` date NOT NULL,
  `image` varchar(255) NOT NULL,
  `id_cat` int(2) DEFAULT NULL,
  PRIMARY KEY (`id_annonce`),
  KEY `id_cat` (`id_cat`),
) ENGINE=InnoDB  DEFAULT CHARSET=latin1;

After linking the foreign key id_cat manually (ON UPDATE SET NULL ON DELETE CASCADE) that's how the db looks like

and after inserting data into Categorie table it looks like this

But unfortunately i couldn't execute this query :

INSERT INTO annonce (id_annonce, titre, description, tarif, deplacement, 
                    date_creation, date_expiration,id_cat) 
VALUES('','anything','anything',2,3,'2017-04-01','2017-04-01',2)

the error says :

1452 - Cannot add or update a child row: a foreign key constraint fails (lametcom.annonce, CONSTRAINT annonce_ibfk_2 FOREIGN KEY (id_cat) REFERENCES annonce (id_cat) ON DELETE SET NULL ON UPDATE CASCADE)

Can anyone help please and so sorry about my poor English i hope you can understand what i mean

inserting an empty string into a not null column. omit that column and let the auto increment worry about it :INSERT INTO annonce (titre, description, tarif, deplacement, date_creation, date_expiration,id_cat) VALUES('anything','anything',2,3,'2017-04-01','2017-04-01',2) — I wrestled a bear once.

Barmar Barmar · Accepted Answer · 2017-01-12T23:37:57

Your foreign key constraint is wrong. You have

FOREIGN KEY id_cat REFERENCES annonce (id_cat)

but it should be:

FOREIGN KEY id_cat REFERENCES categorie (id_cat)

The table name in the foreign key constraint has to be the table you're linking to.

MySQL #1452 - Cannot add or update a child row

1 Answers