RDBMS Design Question


This is in regards to the RDBMS design tutorial on Kirupa.com. On this page here http://www.kirupa.com/developer/php/relational_db_design4.htm, when the author created tbl_works_categories, he said work_id & category_id are foreign keys. I got a bit confused because I did not see anywhere in the code where he defined the foreign key parameter. I just wanted to know if this is a mistake or is it that you don’t need to specify the word “FOREIGN KEY” next to a column…or does MySQL automatically assign them as foreign keys because you used thesame column name?? I just wanted to clear this part up since I’m a bit stuck on that part.