This document discusses converting entity-relationship (E/R) diagrams to relational database schemas. It includes exercises on: 1. Converting a relationship set specifying employee/manager assignments into relational tables. 2. Converting E/R diagrams with weak entity sets and inheritance hierarchies into relational schemas using straight, object-oriented, and nulls approaches. 3. Exercises cover converting E/R diagrams for customer bookings on flights, university course schemas, and family relationships into equivalent relational database designs.

1. Comp 5531 – Files & Databases
Tutorial 5
Winter 2023
Concordia University
Computer Science & Software Engineering
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2. Today’s Plan
From E /R Diagrams to Relational Designs/Models
❖ Converting Weak Entity Sets
❖ Converting isa-hierarchy (of entity sets)
1. Straight E/R-Style Conversion
2. OO Approach
3. Nulls Approach
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3. Converting ER to Relational Model
Exercise 1: a relationship-set named works_for, specifying employee/manager
assignments.
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4. Converting ER to Relational Model
Exercise 1: a relationship-set named works_for, specifying employee/manager
assignments.
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Relational Schema
employee (employee_id, name )
works_for(employee_id, manager_id )
“Many” side is used for primary key.
Relationship involves two copies of EMPLOYEE entity set.

5. Converting ER to Relational Model
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Exercise 2:

6. Converting ER to Relational Model
Relational Schema
job (title, level )
employee (employee-id, employee-name )
branch (branch-name, branch-city, assets )
Works-on (employee-id, branch-name, job-title )
What is the primary key of Works-on?? 6
Exercise 2:

7. E/R Diagram Conversions (Weak Entity Sets)
Exercise 3:Convert this E/R diagram to relational database (Textbook, Ex. 4.5.1).
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8. E/R Conversion > Weak Entity Sets
Relational Database:
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Customers(SSNo, name, addr, phone)
Flights(number, day, aircraft)
Bookings(SSNo, FltNumber, day, row, seat)
What are the Candidate Keys for Bookings?
• {SSNo, FltNumber, day}
• {FltNumber, day, row, seat}

9. E/R Diagram Conversion
Can we describe the weak entity set Bookings using a different
approach?
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10. E/R Diagram Conversion
Exercise 4: Convert the following diagram to a relational database:
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number
Flights
day
Customers
SSNo
name
Booking
addr
aircraft
phone
seat
row

11. E/R Diagram Conversion
Exercise 4: Convert the following diagram to a relational database.
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Customers(SSNo, name, addr, phone)
Flights(number, day, aircraft)
Bookings(SSNo, FltNumber, day, row, seat)
number
Flights
day
Customers
SSNo
name
Booking
addr
aircraft
phone
seat
row

12. E/R Diagram Conversion
Exercise 5: Convert the following diagram to a relational database.
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13. E/R Diagram Conversion
1. Isa-hierarchy using the straight E/R-Style
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Depts (name, chair)
Courses (number, deptName, room)
LabCourses (number, deptName, computerAllocation)

14. E/R Diagram Conversion
2. Isa-hierarchy using the OO Approach
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Depts (name, chair)
Courses (number, deptName, room)
LabCourses (number, deptName, room, computerAllocation)

15. E/R Diagram Conversion
3. Isa-hierarchy using the NULLs Approach:
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Depts (name, chair)
Lab-Courses (number, deptName, room, computerAllocation)

16. E/R Conversion
Exercise 6: Convert the following diagram to a relational database:
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17. E/R Diagram Conversion
1. Isa conversion using E/R –Style
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Person (name, address)
Father (name, address)
Mother (name, address)
Child (name, address)
Married (Wname, Waddress, Hname, Haddress) PK?
Either {Wname, Waddress} OR {Hname, Haddress}
FatherOf (Cname, Caddress, Fname, Faddress)
PK {Cname, Caddress}
MotherOf (Cname, Caddress, Mname, Maddress)
ChildOf (Cname, Caddress, Pname, Paddress) PK?

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Person (name, address)
PersonFather (name, address)
PersonMother (name, address)
PersonChild (name, address)
PersonMotherChild (name, address)
PersonFatherChild (name, address)
PersonMotherFather (name, address) Dose it mean??
PersonMotherFatherChild (name, address) Dose it mean??
Add 4 tables for the 4 diamonds:
ChildOf(personName,personAddress,childName,childAddress)
FatherOf(childName,childAddress,fatherName,fatherAddress)
MotherOf(childName,childAddress,motherName,motherAddress)
Married(husbandName,husbandAddress,wifeName,wifeAddress)
E/R Diagram Conversion
2. Isa conversion using OO Approach
Question: Can we combine the first
four tables??

19. E/R Diagram Conversion
2. Isa conversion using OO Approach
❖ Since in OO each entity can belong to one class only, then the m:1
relationships MotherOf and FatherOf can be added as attributes to
therelations:
PersonChild (name, address, Fname, Faddress, Mname, Maddress)
PersonMotherChild (name, address, Fname, Faddress, Mname, Maddress)
PersonFatherChild (name, address, Fname, Faddress, Mname, Maddress)
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20. E/R Diagram Conversion
2. Isa conversion using OO Approach
❖ Also, Married can be added as attributes to 4 tables; PersonFather, PersonMother, PersonMotherChild,
PersonFatherChild.
❖ Should add spouse name and addrress to these tables (Sname, Saddress)!
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PersonFather (name, address, Sname, Saddress)
PersonMother (name, address, Sname, Saddress)
PersonMotherChild (name, address, Fname, Faddress, Mname,
Maddress, Sname, Saddress)
PersonFatherChild (name, address, Fname, Faddress, Mname,
Maddress, Sname, Saddress)
❖ ChildOf
ChildOf (Cname, Caddress, Pname, Paddress)

21. E/R Diagram Conversion
3. Isa conversion using Nulls Approach
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Person (name, address)
Married (Wname, Waddress, Hname, Haddress)
FatherOf (Cname, Caddress, Fname, Faddress)
MotherOf (Cname, Caddress, Mname, Maddress)
ChildOf (Cname, Caddress, Pname, Paddress)

22. Welcome!