Error Code: 1005. Can't create table '...' (errno: 150)

Question

Error Code: 1005 -- there is a wrong primary key reference in your code

Usually it's due to a referenced foreign key field that does not exist. It might be you have a typo mistake, or check case it should be same, or there's a field-type mismatch. Foreign key-linked fields must match definitions exactly.

Some known causes may be:

1. The two key fields type and/or size doesn’t match exactly. For example, if one is INT(10) the key field needs to be INT as well and not BIGINT or SMALLINT or TINYINT. You should also check that one is not SIGNED and the other is UNSIGNED. They both need to be exactly the same.
2. One of the key field that you are trying to reference does not have an index and/or is not a primary key. If one of the fields in the relationship is not a primary key, you must create an index for that field.
3. The foreign key name is a duplicate of an already existing key. Check that the name of your foreign key is unique within your database. Just add a few random characters to the end of your key name to test for this.
4. One or both of your tables is a MyISAM table. In order to use foreign keys, the tables must both be InnoDB. (Actually, if both tables are MyISAM then you won’t get an error message - it just won’t create the key.) In Query Browser, you can specify the table type.
5. You have specified a cascade ON DELETE SET NULL, but the relevant key field is set to NOT NULL. You can fix this by either changing your cascade or setting the field to allow NULL values.
6. Make sure that the Charset and Collate options are the same both at the table level as well as individual field level for the key columns.
7. You have a default value (that is, default=0) on your foreign key column
8. One of the fields in the relationship is part of a combination (composite) key and does not have its own individual index. Even though the field has an index as part of the composite key, you must create a separate index for only that key field in order to use it in a constraint.
9. You have a syntax error in your ALTER statement or you have mistyped one of the field names in the relationship
10. The name of your foreign key exceeds the maximum length of 64 characters.

For more details, refer to: MySQL Error Number 1005 Can’t create table

This could also happen when exporting your database from one server to another and the tables are listed in alphabetical order by default.
So, your first table could have a foreign key of another table that is yet to be created. In such cases, disable foreign_key_checks and create the database.

Just add the following to your script:

SET FOREIGN_KEY_CHECKS=0;

and it shall work.

Very often it happens when the foreign key and the reference key don't have the same type or same length.

Sometimes it is due to the master table is dropped (maybe by disabling foreign_key_checks), but the foreign key CONSTRAINT still exists in other tables. In my case I had dropped the table and tried to recreate it, but it was throwing the same error for me.

So try dropping all the foreign key CONSTRAINTs from all the tables if there are any and then update or create the table.

I had a similar error. The problem had to do with the child and parent table not having the same charset and collation. This can be fixed by appending ENGINE = InnoDB DEFAULT CHARACTER SET = utf8;

CREATE TABLE IF NOT EXISTS `country` (`id` INT(11) NOT NULL AUTO_INCREMENT,...) ENGINE = InnoDB DEFAULT CHARACTER SET = utf8;

... on the SQL statement means that there is some missing code.

The foreign key has to have the exact same type as the primary key that it references. For the example has the type “INT UNSIGNED NOT NULL” the foreing key also have to “INT UNSIGNED NOT NULL”

CREATE TABLE employees(
id_empl INT UNSIGNED NOT NULL AUTO_INCREMENT,
PRIMARY KEY(id)
);
CREATE TABLE offices(
id_office INT UNSIGNED NOT NULL AUTO_INCREMENT,
id_empl INT UNSIGNED NOT NULL,
PRIMARY KEY(id),
CONSTRAINT `constraint1` FOREIGN KEY (`id_empl`) REFERENCES `employees` (`id_empl`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='my offices';

Error Code: 1005

I had a similar issue, so here are few things that I did try (not in any order, except for the solution :) )

1. Changed the foreign key names (it didn't work)
2. Reduced the foreign key length
3. Verified the datatypes (darn nothing wrong)
4. Check indexes
5. Check the collations (everything fine, darn again)
6. Truncated the table, of no good use
7. Dropped the table and re-created
8. Tried to see if any circular reference is being created --- all fine

9. Finally, I saw that I had two editors open. One that in PhpStorm (JetBrains) and the other MySQL workbench. It seems that the PhpStorm / MySQL Workbench creates some kind of edit lock.

   I closed PhpStorm just to check if locking was the case (it could have been the other way around). This solved my problem.