Second Normal Form (2NF) in DBMS Theory - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main goal of Second Normal Form (2NF)?

The main goal of 2NF is to remove partial dependencies, meaning every non-key attribute must depend on the whole primary key, not just part of it.

beginner

What kind of dependency does 2NF eliminate?

2NF eliminates partial dependency, where a non-key attribute depends only on a part of a composite primary key.

beginner

True or False: A table with a single-column primary key is always in 2NF.

True. Since there is no composite key, partial dependency cannot exist, so the table is automatically in 2NF if it is in 1NF.

intermediate

Why is 2NF important in database design?

2NF helps reduce data redundancy and update anomalies by ensuring that attributes depend on the entire primary key, making data more consistent.

beginner

What must a table satisfy before it can be in Second Normal Form?

It must first be in First Normal Form (1NF), meaning it has no repeating groups and each field contains atomic values.

Which of the following best describes a table in 2NF?

A No transitive dependency

B No repeating groups or arrays

C No partial dependency on any part of the primary key

D No foreign keys

2NF requires that every non-key attribute depends on the whole primary key, eliminating partial dependencies.

If a table has a single-column primary key, it is:

A Always in 2NF

B Never in 2NF

C Only in 1NF

D Only in 3NF

With a single-column primary key, partial dependency cannot exist, so the table is always in 2NF if it is in 1NF.

What problem does 2NF mainly address?

A Partial dependency

B Transitive dependency

C Duplicate rows

D Missing primary key

2NF removes partial dependencies where attributes depend on part of a composite key.

Before applying 2NF, a table must be in which normal form?

A 4NF

B 3NF

C BCNF

D 1NF

2NF builds on 1NF, so the table must first be in First Normal Form.

Which of these is a sign that a table is NOT in 2NF?

A All attributes depend on the whole key

B A non-key attribute depends only on part of a composite key

C No repeating groups

D No null values

Partial dependency means a non-key attribute depends on only part of the composite key, violating 2NF.

Explain what Second Normal Form (2NF) means and why it is important in database design.

Think about how attributes relate to the whole primary key.

Describe the steps to check if a table is in Second Normal Form (2NF).

Start from 1NF and focus on dependencies.