MySQL “ERROR 1005 (HY000): Can't create table 'foo.#sql-12c_4' (errno: 150)”

Question

I was working on creating some tables in database foo, but every time I end up with errno 150 regarding the foreign key. Firstly, here\'s my code for creating t

Answer 1

I was using a duplicate Foreign Key Name.

Renaming the FK name solved my problem.

Clarification:

Both tables had a constraint called PK1, FK1, etc. Renaming them/making the names unique solved the problem.

Answer 2

check to make the field you are referencing to is an exact match with foreign key, in my case one was unsigned and the other was signed so i just changed them to match and this worked

ALTER TABLE customer_information ADD CONSTRAINT fk_customer_information1 FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE ON UPDATE CASCADE

Answer 3

I use Ubuntu linux, and in my case the error was caused by incorrect statement syntax (which I found out by typing perror 150 at the terminal, which gives

MySQL error code 150: Foreign key constraint is incorrectly formed

Changing the syntax of the query from

alter table scale add constraint foreign key (year_id) references year.id;

to

alter table scale add constraint foreign key (year_id) references year(id);

fixed it.

Answer 4

The referenced column must be an index of a single column or the first column in multi column index, and the same type and the same collation.

My two tables have the different collations. It can be shown by issuing show table status like table_name and collation can be changed by issuing alter table table_name convert to character set utf8.

Answer 5

You should make car_id a primary key in cars.

Answer 6

The referenced field must be a "Key" in the referenced table, not necessarily a primary key. So the "car_id" should either be a primary key or be defined with NOT NULL and UNIQUE constraints in the "Cars" table.

And moreover, both fields must be of the same type and collation.