University of Toronto CSC343, Winter 2021
ER Diagrams: Solutions
1. Consider the following ER diagram:
start’
phone’ (0,1)’ member’ (1,N)’ CID’
person’
club’
name’
Caddress’
Which of these cardinalities is possible?
|person|
|member|
|club|
Is it possible?
5
0
8
Yes
No
5
7
8
Yes
No
5
0
5
Yes
No
5
10
5
Yes
No
11
3
4
Yes
No
11
9
4
Yes
No
2. Below is an Entity-Relationship diagram about car dealerships. It may or may not represent the domain well. Answer the questions below.
VIN model
year
name
email phone
car
date amount
customer
(0,1)
sale
(0, N)
(1,N)
works at
(1,1)
dID dName
salary
sID sName
(0, N)
salesperson
dealership
(a) A car sale cannot involve more than one salesperson.
False
(b) There can be two cars with the same VIN as long as the model and year are different.
True
(c) A salesperson can work at any number of dealerships.
True
(d) There can¡¯t be more salespeople than dealerships.
True
(e) There can be multiple sales on the same date.
False
(f) Two salespeople can have the same sID as long as they work at different dealerships.
True
(g) This model contains a weak entity set.
True
(h) The works at relationship is a one-to-many relationship.
False
True
False
False
False
True
False
False
True