Normal Form Where Every Non-Prime Attribute Is Fully Dependent on Prime Attribute

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Nov 3, 2026

You are asking which normal form corresponds to the constraint:

“A normal form in which every non-prime attribute is fully dependent on prime attribute.”

To interpret this precisely in relational database theory, we need the common definitions:

prime attribute (sometimes called a “key attribute”)
non-prime attribute
full functional dependency
functional dependency

Intuitively, “fully dependent on prime attribute” targets partial dependency (where a non-prime attribute depends on only part of a composite key). This is the hallmark requirement that distinguishes 2NF from 1NF and is weaker/stronger than other normal forms in different ways.

A practical dependency-focused way to remember it:

1NF: atomic values (no repeating groups).
2NF: remove partial dependency of non-prime attributes on proper subsets of a composite candidate key.
3NF: remove transitive dependency of non-prime attributes on the candidate key.
BCNF (Boyce-Codd normal form): strengthens 3NF by requiring determinants to be superkeys even for certain cases where 3NF would still allow a violation.

Below, we map your phrase to the standard normal-form definition used in database courses.

Normalization: 1NF, 2NF, 3NF (Concepts + Examples)

Key idea: partial dependency is the thing “fully dependent on prime attribute” eliminates

Consider a relation $R(A,B,C,\dots)$ with a composite candidate key (prime attributes) such as $K = AB$ .
A non-prime attribute $C$ can have these patterns:

Partial dependency (bad for 2NF): $AB \to C$ holds, but also $A \to C$ or $B \to C$ .
Full dependency (good for 2NF): $AB \to C$ holds, and neither $A \to C$ nor $B \to C$ holds (only the whole key determines $C$ ).

“Every non-prime attribute is fully dependent on prime attributes” is exactly the restriction:

no non-prime attribute may depend on a proper subset of a composite candidate key.

That is the canonical textbook condition for 2NF.

How the normal forms progressively restrict dependencies

Atomicity requirement

1NF

Eliminate repeating groups; ensure each field is atomic."

No partial dependency

2NF

If keys are composite, non-prime attributes depend on the whole key."

No transitive dependency

3NF

Non-prime attributes don’t depend on other non-prime attributes."

Stricter determinant condition

BCNF

Every non-trivial FD’s determinant must be a superkey."

Decision mapping to your multiple-choice options

Your question offers:

(i) 1 NF
(ii) 2 NF
(iii) 3 NF
(iv) BCNF

The phrase “every non-prime attribute is fully dependent on prime attribute” is directly the definition-level condition that characterizes Second Normal Form.

So the correct answer is:

✅ (ii) 2 NF

Why it is 2NF (dependency-pattern check)

1
Step 1
2NF assumes the relation is already in 1NF (atomic attributes).
2
Step 2
Find candidate keys; the attributes in these keys are prime attributes.
3
Step 3
If a candidate key is composite (e.g., $AB$ ), check each proper subset ( $A$ and $B$ ).
4
Step 4
For every non-prime attribute $C$ , verify there is no functional dependency like $A \to C$ or $B \to C$ (unless $A$ or $B$ is itself a superkey).
5
Step 5
If all non-prime attributes depend only on the whole composite key (not on its parts), the relation satisfies 2NF.

Mermaid: dependency types vs which normal form removes them

Partial dependency is what your “fully dependent” wording targets → 2NF.
Transitive dependency (typically captured in 3NF/BCNF discussions) is a different condition.

Which normal form corresponds to each dependency concept?

Your phrase focuses specifically on partial dependency.

Pro Tip: translate the phrase into a dependency statement

Read “fully dependent on prime attribute” as: for composite candidate keys, non-prime attributes must depend on the entire key, not on any proper subset.

Common misconception: not 3NF or BCNF

3NF and BCNF are about transitive dependencies and determinant/superkey constraints. Your phrase explicitly targets partial dependency, which is the defining concern of 2NF.

FAQ: How to distinguish 2NF vs 3NF vs BCNF quickly

Normal Form Flashcards

1 / 5

Question · Term

Prime attribute

Click to reveal

Answer · Definition

An attribute that appears in at least one candidate key.

Knowledge Check

Question 1 of 4

Q1Single choice

A relation has a composite candidate key $AB$ and a non-prime attribute $C$ such that $A \to C$ holds. Which normal form is violated (assuming 1NF holds)?

1NF

2NF

3NF

BCNF

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