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

Subtle, but this error got me because I forgot to declare a smallint column as unsigned to match the referenced, existing table which was "smallint unsigned." Having one unsigned and one not unsigned caused MySQL to prevent the foreign key from being created on the new table.

id smallint(3) not null

does not match, for the sake of foreign keys,

id smallint(3) unsigned not null