Category: MariaDB

How to fix (errno: 150 “Foreign key constraint is incorrectly formed”) MySQL, MariaDB

If you catch errno: 150 “Foreign key constraint is incorrectly formed” when you try to create a new table in mySQL(or another relational DB) then you can use a simple way to find a bad foreign key(s). Just execute this query:

SELECT
  CONSTRAINT_NAME, 
  TABLE_NAME, 
  COLUMN_NAME, 
  REFERENCED_TABLE_NAME, 
  REFERENCED_COLUMN_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE
  REFERENCED_TABLE_NAME = '<your table name here>' OR TABLE_NAME = '<your table name here>';

After that you can see where this bad table using and you can go and delete bad foreign key(s).

Happy SQLing)