InnoDB foreign key definition cannot resolve column name - mysql

Question

I have a problem creating a foreign key constraint between two tables.
Here is the first table:
CREATE TABLE `agews_rifiuti_cer` (
`id_cer` int(10) unsigned NOT NULL AUTO_INCREMENT,
`agews_id` int(10) unsigned DEFAULT '0',
`livello` tinyint(4) DEFAULT '1',
`codice` varchar(10) DEFAULT NULL,
`descrizione` varchar(255) DEFAULT NULL,
`note` text,
`flag_pericoloso` tinyint(1) DEFAULT '0',
`id_cliente` int(10) unsigned DEFAULT '1',
`flag_modificato` char(1) DEFAULT 'N',
PRIMARY KEY (`id_cer`),
KEY `fk_id_cliente_agews_sgs_codici_cer` (`id_cliente`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
And here is the second one:
CREATE TABLE `lin_98_47_rifiuti` (
`id_rifiuto` int(10) unsigned NOT NULL AUTO_INCREMENT,
`id_azienda` int(10) unsigned NOT NULL DEFAULT '1',
`id_sede` int(10) unsigned NOT NULL DEFAULT '1',
`revisione_documento` int(10) unsigned NOT NULL DEFAULT '0',
`rifiuto` varchar(255) DEFAULT NULL,
`codice_cer` varchar(10) DEFAULT NULL,
`nome_interno` varchar(255) DEFAULT NULL,
`descrizione` text,
`materie_prime` text,
`contenitore` text,
`deposito` text,
`data_ultima_analisi` date DEFAULT NULL,
`stato_fisico` enum('Solido pulverulento','Solido non pulverulento','Fangoso palabile','Liquido') DEFAULT 'Solido non pulverulento',
`quantita` float(9,1) DEFAULT '0.0',
`unita_misura` enum('Kg','l','mc') DEFAULT 'Kg',
`id_pericolo` int(10) unsigned DEFAULT NULL,
`destino` enum('Recupero','Smaltimento') DEFAULT NULL,
`id_recupero` int(10) unsigned DEFAULT NULL,
`id_smaltimento` int(10) unsigned DEFAULT NULL,
`id_cer` int(10) unsigned DEFAULT NULL,
`immagine` varchar(255) DEFAULT NULL,
`image_type` varchar(20) DEFAULT NULL,
`image_content` mediumblob,
`image_size_x` smallint(5) unsigned DEFAULT '0',
`image_size_y` smallint(5) unsigned DEFAULT '0',
`flag_storico` tinyint(1) DEFAULT '0',
`id_responsabile` int(10) unsigned DEFAULT '0',
`nome_responsabile` varchar(255) DEFAULT '0',
`id_ultima_modifica` int(10) unsigned DEFAULT '0',
`create_log` tinyint(1) DEFAULT '1',
PRIMARY KEY (`id_rifiuto`,`id_azienda`,`id_sede`,`revisione_documento`),
KEY `fk_main_lin_98_47_rifiuti` (`id_azienda`,`id_sede`,`revisione_documento`),
KEY `fk_id_responsabile_lin_98_47_rifiuti` (`id_responsabile`,`id_azienda`,`id_sede`,`revisione_documento`,`nome_responsabile`),
KEY `fk_id_pericolo_lin_98_47_rifiuti` (`id_pericolo`),
KEY `fk_id_recupero_lin_98_47_rifiuti` (`id_recupero`),
KEY `fk_id_smaltimento_lin_98_47_rifiuti` (`id_smaltimento`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
The problem happens the I try to do this:
ALTER TABLE lin_98_47_rifiuti ADD CONSTRAINT fk_id_cer_lin_98_47_rifiuti FOREIGN KEY (id_cer) REFERENCES agews_rifiuti_cer(id_cer) ON UPDATE CASCADE ON DELETE CASCADE;
And I get this error:
#1005 - Can't create table 'db_626suite.#sql-71c_13d5' (errno: 150)
While the command SHOW INNODB STATUS says:
Error in foreign key constraint of table db_626suite/#sql-71c_13d5:
FOREIGN KEY (id_cer) REFERENCES agews_rifiuti_cer(id_cer) ON UPDATE CASCADE ON DELETE CASCADE:
Cannot resolve column name close to:
) ON UPDATE CASCADE ON DELETE CASCADE
But the syntax and fields definitions seem correct to me. What am I doing wrong?
EDIT:
Marc B suggested that it could be due to the fact that id_cer is defined as NOT NULL in agews_rifiuti_cer, but I do not think this is the case, in fact please consider this other table:
CREATE TABLE `agews_rifiuti_pericolo` (
`id_pericolo` int(10) unsigned NOT NULL AUTO_INCREMENT,
`agews_id` int(10) unsigned DEFAULT '0',
`codice` varchar(255) DEFAULT NULL,
`pericolo` varchar(255) DEFAULT NULL,
`note` text,
`id_cliente` int(10) unsigned DEFAULT '1',
`flag_modificato` char(1) DEFAULT 'N',
PRIMARY KEY (`id_pericolo`),
KEY `codice_rifiuti_recupero` (`codice`),
KEY `fk_id_cliente_rifiuti_pericolo` (`id_cliente`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Here id_pericolo is defined as NOT NULL as id_cer above, and yet this works perfectly:
ALTER TABLE lin_98_47_rifiuti ADD CONSTRAINT fk_id_pericolo_lin_98_47_rifiuti FOREIGN KEY (id_pericolo) REFERENCES agews_rifiuti_pericolo(id_pericolo) ON UPDATE CASCADE ON DELETE SET NULL;
even if in lin_98_47_rifiuti the field id_pericolo is defined as DEFAULT NULL
EDIT 2:
I just tried this minimal setup:
CREATE TABLE `cer` (
`id_cer` int(10) unsigned NOT NULL AUTO_INCREMENT,
`codice` varchar(10) DEFAULT NULL,
PRIMARY KEY (`id_cer`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
CREATE TABLE `rifiuti` (
`id_rifiuto` int(10) unsigned NOT NULL AUTO_INCREMENT,
`id_cer` int(10) unsigned NULL DEFAULT NULL,
`rifiuto` varchar(10) DEFAULT NULL,
PRIMARY KEY (`id_rifiuto`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
ALTER TABLE rifiuti ADD FOREIGN KEY (id_cer) REFERENCES cer(id_cer) ON UPDATE CASCADE ON DELETE CASCADE;
and it all worked correctly, yet I do not understand what the problem might be in my original query.
Also I think this proves that is not a matter of defining the fields as NOT NULL or DEFAULT NULL.

Answer 1

You've defined id_cer as default null in the lin_98_47 table, but the matching FK field in the other table is defined as not null.
The field definitions have to match EXACTLY for a foreign key relationship to be established, and that includes nullability:
`id_cer` int(10) unsigned NOT NULL AUTO_INCREMENT,
`id_cer` int(10) unsigned DEFAULT NULL,

Answer 2

I really do not understand why, but renaming id_cer to id_codice in all tables, while leaving its definition unaltered, has solved the problem.
So it would seem that MySQL had some kind of problem with that specific field name.