Question

I have the following two tables:

CREATE TABLE `table1` (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  `CODE` varchar(30) COLLATE utf8_bin NOT NULL,
  `LANG` varbinary(30) NOT NULL,
  `NAME` varchar(255) COLLATE utf8_bin NOT NULL,
  PRIMARY KEY (`ID`),
  KEY `NewIndex1` (`CODE`)
) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8 COLLATE=utf8_bin

and

CREATE TABLE `table2` (
  `ID` int(11) NOT NULL AUTO_INCREMENT,
  `TABLE1_CODE` varchar(30) NOT NULL,
  `SOME_ADD` varchar(30) DEFAULT NULL,
  PRIMARY KEY (`ID`)
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8

and I am trying to make a reference with:

alter table `factorydb`.`table2` add constraint `FK_table2` FOREIGN KEY (`TABLE1_CODE`) REFERENCES `table1` (`CODE`)

I get the error:

Can't create table 'factorydb.#sql-70c_306' (errno: 150)

The idea is to deal with language entries in my tables, so that I will have some values in table1 as

ID | CODE   | LANG | NAME
1   CARCODE    EN    Car
2   CARCODE    DE    Auto

And I want to make a reference to the CODE in table1 as for me both CARCODE values are valid, only depending on the language settings.

I am doing it wrong?

All help is appreciated.

Answer 1

Both the columns in the foreign key, must be the same type, length AND collation.

Btw, you really want to prefer setting a foreign key on integers instead of varchars, it’s much faster joining and takes less space