MySQL. Can't create table errno 150

Question

I have to create a database with two tables in MySQL, but the script fails with errno 150 (foreign key problem). I double-checked the foreign key fields to be the same on bo

Answer 1

While working with MySQL Workbench and MySQL 5.5.27, I have encountered the similar problem. In my case issue was with INT type fields. Erroneously in one table it was INT UNSIGNED and in referencing table it was INT.

Answer 2

table1.field1 has no index defined on it.

It is required to place a FOREIGN KEY constraint on field1.

With this:

 CREATE  TABLE IF NOT EXISTS `testdb`.`table1` (
   `id` INT UNSIGNED NOT NULL ,
   `field1` VARCHAR(50) NULL ,
   KEY ix_table1_field1 (field1),
   PRIMARY KEY (`id`) )
 ENGINE = InnoDB;

Everything should then work as expected.

Answer 3

Another hint:

Even when your data types seem to be the same - in my case both columns had VARCHAR(50) - this is not enough.

You also need to make sure that both columns have the same COLLATION.

Answer 4

For me, the problem was with using CONSTRAINT in the CREATE TABLE query.

Answer 5

MySQL will also throw this error if your mistyping the name of the referring table. I pulled my hair out for awhile until I realized I missed a letter in foreign key (column1) references mistyped_table(column1)

Answer 6

When I had this problem it was because I had set the id in the first table to be unsigned whereas the foreign key in the second table was not. Making them both unsigned fixed it for me.