- First, you cannot have two FK on the same column.
- Second, it's totally bad design to have a table for each automaker.
What you should do is have one
AUTO_MAKER table with the folowing columns:
Such a table will have as many rows as automakers you decide to have in your database, one automaker for row.
Then, in the
CAR table create a column
maker_id with a FK to
AUTOMAKER'S PK. Such a column could allow
NULL in case you don't know the automaker at the moment of inserting a row in
CAR. Or it could not allow
NULL if you want to be strict, so forcing users to only insert cars with known and existing automakers (existing in the AUTO_MAKER table).
By the way, the question is RDBMS agnostic.