4.3. 2nd Normal Form

• All data must depend on the Primary Key

• All attributes (non-key columns) dependent on the key (PK)

4.3.1. Problem

Table 4.9. assignments

id (PK)	firstname	lastname	year	mission
1	Melissa	Lewis	2035	Ares3
2	Mark	Watney	2035	Ares3
3	Rick	Martinez	2035	Ares3

4.3.2. Solution

Table 4.10. astronauts

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

Table 4.11. missions

id (PK)	year	mission
1	2031	Ares1
2	2033	Ares2
3	2035	Ares3

Table 4.12. assignments

id (PK)	astronaut_id (FK)	mission_id (FK)
1	1	3
1	2	3
1	3	3

Figure 4.10. All data must depend on the Primary Key. Image credit: [1]

4.3.3. Recap

Figure 4.11. If all data depend on the Primary Key the database achieved 2nd Normal Form.

4.3.4. References

[1]

Lowgren, Jesper. Database Normalization 1NF 2NF 3NF. Year: 2021. Retrieved: 2022-02-05. URL: https://www.youtube.com/watch?v=SK4H5tTT6-M