MySQL Creating tables with Foreign Keys giving errno: 150

Question

I am trying to create a table in MySQL with two foreign keys, which reference the primary keys in 2 other tables, but I am getting an errno: 150 error and it will not create

Answer 1

(Side notes too big for a Comment)

There is no need for an AUTO_INCREMENT id in a mapping table; get rid of it.

Change the PRIMARY KEY to (role_id, role_group_id) (in either order). This will make accesses faster.

Since you probably want to map both directions, also add an INDEX with those two columns in the opposite order. (There is no need to make it UNIQUE.)

More tips: http://mysql.rjweb.org/doc.php/index_cookbook_mysql#speeding_up_wp_postmeta