4.5. 4th Normal Form

• No multi-valued dependencies

4.5.1. Problem

Table 4.18. astronauts

id (PK)	firstname	lastname	email
1	Melissa	Lewis	mlewis@nasa.gov
1	Melissa	Lewis	mlewis@gmail.com
2	Mark	Watney	mwatney@nasa.gov
3	Rick	Martinez	rmartinez@nasa.gov

Note, that Melissa has two emails: work email mlewis@nasa.gov and private email mlewis@gmail.com.

4.5.2. Solution

Table 4.19. astronauts

id (PK)	firstname	lastname
1	Melissa	Lewis
2	Mark	Watney
3	Rick	Martinez

Table 4.20. astronaut_emails

id (PK)	email	astronaut_id (FK)
1	mlewis@nasa.gov	1
2	mlewis@gmail.com	1
3	mwatney@nasa.gov	2
4	rmartinez@nasa.gov	3