Re: ERROR 1005: Can't create table (errno: 150) :: InnoDB

[Edwin Dando]

Ok, here is what I have found after hours of ripping my hair out with this!

As other posters have said, both tables must be INNODB. The foreign key field must have an index on it. The foeign key field and the field being referenced must be of the same type (I only use integer) and, after hours of pain, they must be UNSIGNED.

Here is some example code (this is for a recruitment website). Firstly, there are two tables that dont reference each other, s_user and skillset.


DROP TABLE IF EXISTS s_user;
CREATE TABLE s_user (
id_s_user INTEGER UNSIGNED NOT NULL AUTO_INCREMENT,
username VARCHAR(20) NOT NULL UNIQUE,
password VARCHAR(20) NOT NULL,
fname VARCHAR(50) NOT NULL,
lname VARCHAR(50) NOT NULL,
email VARCHAR(40) NOT NULL,
PRIMARY KEY(id_s_user)
)TYPE=InnoDB;

DROP TABLE IF EXISTS skillset;
CREATE TABLE skillset (
id_skillset INTEGER UNSIGNED NOT NULL AUTO_INCREMENT,
skillset_name VARCHAR(50) NOT NULL UNIQUE,
PRIMARY KEY(id_skillset)
)TYPE=InnoDB;


I know have a table that represents the one to many relationship from s_user to skillset (a user can have many skillsets, for example, a user can know java, php, c++ etc).

DROP TABLE IF EXISTS user_skillset;
CREATE TABLE user_skillset(
id_s_user INTEGER UNSIGNED NOT NULL, INDEX id_s_user_ind (id_s_user),
id_skillset INTEGER UNSIGNED NOT NULL, INDEX id_skillset_ind (id_skillset),
PRIMARY KEY(id_s_user, id_skillset),
FOREIGN KEY(id_s_user) REFERENCES s_user(id_s_user) ON DELETE CASCADE ON UPDATE CASCADE,
FOREIGN KEY(id_skillset) REFERENCES skillset(id_skillset) ON DELETE CASCADE ON UPDATE CASCADE
)TYPE=InnoDB;


Note both FK fields have indexes, and both also use unsigned integers. Also dont forget to create the table being referenced _before_ the one doing the referencing, otherwise there wont be anything to reference!

Hope this helps.