Cracking the Coding Interview, 4 Edition - 150 Programming Interview Questions and Solutions

Solutions to Chapter 15 | Databases
15.4 Draw an entity-relationship diagram for a database with companies, people, and professionals
(people who work for companies).
SOLUTION
pg 80
People who work for companies are Professionals. So there is an ISA (is a) relationship between
People and Professionals (or we could say that a Professional is derived from People).
Each Professional has additional information such as degree, work experiences, etc, in addition
to the properties derived from People.
A Professional works for one company at a time, but Companies can hire many Professionals,
so there is a Many to One relationship between Professionals and Companies. This “Works
For” relationship can store attributes such as date of joining the company, salary, etc. These
attributes are only defined when we relate a Professional with a Company.
A Person can have multiple phone numbers, which is why Phone is a multi-valued attribute.
PName
Sex
DOB
Phone
PID
Address
People
ISA
Date of
Joining
CID
CName
Professional
N
Works For
1
Companies
Degree
Experience
Salary
Address
2 3 5
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