The document discusses entity occurrence diagrams and how they are used to determine the cardinality between entities. It provides examples of a car hire entity occurrence diagram and a capital cities entity occurrence diagram. The car hire diagram shows a one-to-many relationship between bookings and customers, as one customer can have multiple bookings but each booking is for only one customer. The capital cities diagram shows a one-to-one relationship between countries and their capital cities, as each country has one capital city and each capital city is only associated with one country.

1. ENTITY OCCURRENCE DIAGRAMS
Higher Computing Science

2. ENTITY OCCURRENCE DIAGRAMS
• Entity occurrence diagrams are used to determine the cardinality
between entities.
• The cardinality can be one of three types:
• One-to one (1:1)
• One-to-many(1:m)
• Many-to-many (m:n)

3. CAR HIRE EXAMPLE
Customer ID Name
C001 James Green
C002 Hassan Shad
C003 Mike Fraser
C004 Anna Richards
Booking Ref Customer ID Registration Date
B3481 C003 BA18 HER 17/04/20
B3489 C002 BE57 GGV 16/05/20
B3490 C004 LC19 HTR 03/01/20
B3524 C002 LD59 HHT 18/03/20
B3537 C001 SK18 UBG 05/03/20
B3562 C003 ST58 PLK 10/04/20
B3563 C002 SK18 UBG 02/04/20
Booking Customer

4. CAR HIRE EXAMPLE
• Step 1 - Draw the entities
CustomerBooking
Booking Ref Customer ID
B3481 C003
B3489 C002
B3490 C004
B3524 C002
B3537 C001
B3562 C003
B3563 C002

5. CAR HIRE EXAMPLE
• Step 2 - Add in the primary key from each table row
B348
1B348
9B349
0B352
4B353
7B356
2B356
3
C001
C002
C003
C004
Booking Ref Customer ID
B3481 C003
B3489 C002
B3490 C004
B3524 C002
B3537 C001
B3562 C003
B3563 C002
CustomerBooking

6. CAR HIRE EXAMPLE
• Step 3 – Map entity relationships by drawing a line between associated
entity occurrences
B348
1B348
9B349
0B352
4B353
7B356
2B356
3
C001
C002
C003
C004
Booking Ref Customer ID
B3481 C003
B3489 C002
B3490 C004
B3524 C002
B3537 C001
B3562 C003
B3563 C002
CustomerBooking

7. CAR HIRE EXAMPLE
• Step 3 – Map entity relationships by drawing a line between associated
entity occurrences
B348
1B348
9B349
0B352
4B353
7B356
2B356
3
C001
C002
C003
C004
Booking Ref Customer ID
B3481 C003
B3489 C002
B3490 C004
B3524 C002
B3537 C001
B3562 C003
B3563 C002
CustomerBooking

8. CAR HIRE EXAMPLE
• Step 3 – Map entity relationships by drawing a line between associated
entity occurrences
B348
1B348
9B349
0B352
4B353
7B356
2B356
3
C001
C002
C003
C004
Booking Ref Customer ID
B3481 C003
B3489 C002
B3490 C004
B3524 C002
B3537 C001
B3562 C003
B3563 C002
CustomerBooking

9. CAR HIRE EXAMPLE
We can tell from the diagram that a booking can only be placed by one
customer, but a customer can place many bookings.
B348
1B348
9B349
0B352
4B353
7B356
2B356
3
C001
C002
C003
C004
CustomerBooking

10. CAR HIRE EXAMPLE
We can tell from the diagram that a booking can only be placed by one
customer, but a customer can place many bookings.
Booking
places
Customer
One-to-many
relationship

11. CAPITAL CITIES EXAMPLE
City ID Name
X001 Edinburgh
X002 London
X003 Paris
X004 Berlin
Country ID Name Capital City Language
CY-105 England X002 English
CY-003 France X003 French
CY-006 Scotland X001 English
CY-007 Germany X004 German
Country City

12. CAPITAL CITIES EXAMPLE
Country ID City ID
CY-105 X002
CY-003 X003
CY-006 X001
CY-007 X004
CY-105
CY-003
CY-006
CY-007
X001
X002
X003
X004
From the diagram, each country has only one capital city, and each capital
city is the capital of only one country.
CityCountry

13. CAPITAL CITIES EXAMPLE
From the diagram, each country has only one capital city, and each capital
city is the capital of only one country.
City
has the
capitalCountry
One-to-one
relationship