Role of the .frm File

MySQL stores its data dictionary information for tables in .frm files in database directories. This is true for all MySQL storage engines, but every InnoDB table also has its own entry in the InnoDB internal data dictionary inside the tablespace. When MySQL drops a table or a database, it has to delete one or more .frm files as well as the corresponding entries inside the InnoDB data dictionary. Consequently, you cannot move InnoDB tables between databases simply by moving the .frm files.