Examples of Keys
•Product(name, price, category, color)
–name, category à price
–category à color
–
–Keys are:    {name, category} and all supersets
–
•Enrollment(student, address, course, room, time)
–student à address
–room, time à course
–student, course à room, time
–
–Keys are:  [in class]
Keys: {student, room, time},  {student, course}  and all supersets