Database Normalization

Question 1

Which Normal Form ensures that there are no "transitive dependencies" (e.g., A depends on Primary Key B, but C depends on A)?

Accepted Answer

3NF — Third Normal Form (3NF) dictates that every non-key column must depend directly on the primary key, and not on another non-key column.

Question 2

The primary goal of database normalization is to…

Accepted Answer

Reduce redundancy and anomalies — Normalization organizes tables so each fact is stored once, preventing inconsistencies and saving space.

Question 3

Normalization eliminates which problems?

Accepted Answer

Insert/update/delete anomalies — Redundancy causes anomalies (e.g. updating a value in one place but not another); normalization removes these by structuring data properly.

Question 4

First Normal Form (1NF) requires that…

Accepted Answer

Each column holds atomic values — 1NF forbids multi-valued/repeating fields; each cell contains a single value, making the data tabular and queryable.

Question 5

Second Normal Form (2NF) requires 1NF plus…

Accepted Answer

No partial dependency on any PK — 2NF removes attributes that depend on only part of a composite key, moving them to their own table.

Question 6

Third Normal Form (3NF) requires 2NF plus…

Accepted Answer

No transitive dependency on non-keys — 3NF removes indirect dependencies (A→B→C), so every non-key attribute depends directly on the primary key.

Question 7

A functional dependency A → B means…

Accepted Answer

Each A value maps to one B value — Functional dependencies describe how attributes relate; normalization uses them to decide how to decompose tables correctly.

Question 8

DENORMALIZATION intentionally introduces redundancy to…

Accepted Answer

Improve reads by avoiding joins — In read-heavy systems, duplicating/precomputing data speeds queries — trading integrity/space for performance (the reverse of normalization).

Question 9

The main TRADE-OFF normalization makes is…

Accepted Answer

Data integrity versus more table joins — Highly normalized schemas avoid redundancy but require joining many tables for queries; denormalization eases reads at integrity's expense.

Question 10

An UPDATE anomaly (from redundancy) is when…

Accepted Answer

One fact requires many row updates — If a value is duplicated across rows, updating only some leaves the data inconsistent — normalization stores it once to prevent this.

OrderID	Customer	Items (Product, Price, Category)
1	Alice	['Laptop, 1000, Tech', 'Mouse, 50, Tech']
2	Bob	['Desk, 300, Furniture']

Unnormalized Form (UNF)

Problem: Non-Atomic Values

Which normal form does it break?

Test your knowledge

Which Normal Form ensures that there are no "transitive dependencies" (e.g., A depends on Primary Key B, but C depends on A)?

The short version

In more depth

Database Normalization

The Forms

Interview Questions

References & Further Reading

Related topics

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