Solution :
ENTITY 1 CARDINALITY RATIO ENTITY 2
1. Student 1 to many Social security card
A student may have more than one
social security card (legally with the
same unique social security number),
and every social security number belongs
to a unique.
2. Student Many to Many Teacher
Generally students are taught by many
teachers and a teacher teaches many students.
3.ClassRoom Many to Many Wall
Do not forget that the wall is usually
shared by adjacent rooms.
4. Country 1 to 1 Current President
Assuming a normal country under normal
circumstances having one president at a
time.
5. Course Many to Many TextBook
A course may have many textbooks and
text book may be prescribed for different
courses.
6. Item Many to Many Order
Assuming the same item can appear
in different orders.
7. Student Many to Many Class
One student may take several classes.
Every class usually has several students.
8. Class Many to 1 Instructor
Assuming that every class has a unique
instructor. In case instructors were allowed
to team teach, this will be many-many.
9. Instructor 1 to 1 Office
Assuming every instructor has only one
office and it is not shared. In case of offices
shared by 2 instructors, the relationship
will be 2-1. Conversely, if any instructor has a joint
appointment and offices in both departments,
then the relationship will be 1-2. In a very general
case, it may be many-many.
10. E-bay Auction item 1-Many E-bay bid
1 item has many bids and a bid is unique
to an item.
