How is FOREIGN KEY commands different from PRIMARY KEY command ?

Q. How is FOREIGN KEY commands different from PRIMARY KEY command?

Answer =

1. Primary key can not accept null values . while foreign key can accept multiple null values .

2. only one primary key in a table while more than one foreign key in a table .

3. primary key uniquely identify a record in the table while foreign key is a field in the table that is primary key in another table.