First normal form (1NF) and multivalued attributes If a relation has no multivalued attributes and contains only atomic values in each column, the relation is in which normal form?

Difficulty: Easy

Correct Answer: First normal form (1NF)

Explanation:


Introduction / Context:
Normalization is a stepwise method for improving relational design by eliminating redundancy and anomalies. The very first step, First Normal Form (1NF), requires that each field contain only atomic (indivisible) values and that there are no repeating groups or multivalued attributes stored in a single column.


Given Data / Assumptions:

  • The relation stores one value per attribute per row (atomicity).
  • No column contains lists, arrays, or delimited multiple values.
  • There are no repeating group columns that vary in count across rows.


Concept / Approach:

1NF focuses on atomicity and tabular integrity: rows and columns form a simple table where each intersection holds one value of the appropriate domain. Eliminating multivalued attributes often requires moving them into separate rows or a related child table to preserve atomicity and support efficient querying and indexing.


Step-by-Step Solution:

Inspect each attribute to ensure it stores a single value per row.Identify any repeating groups or multivalued fields (for example, phone_numbers).Refactor multivalued attributes into a child relation (for example, PersonPhone with one row per number).Confirm that after refactoring, the table meets 1NF requirements.


Verification / Alternative check:

Normalization theory defines 1NF precisely as the absence of repeating groups and multivalued attributes. Higher normal forms (2NF, 3NF, BCNF, 4NF) address functional and multivalued dependencies beyond atomicity but assume 1NF as a prerequisite.


Why Other Options Are Wrong:

  • 2NF and 3NF address partial and transitive dependencies and presuppose 1NF.
  • BCNF refines 3NF with stricter determinant rules.
  • 4NF addresses nontrivial multivalued dependencies but still assumes 1NF first.


Common Pitfalls:

  • Keeping comma-separated lists in a single column, which breaks indexing and constraints.
  • Confusing composite attributes with multivalued ones; composite can be split into components, but must still store one value per component.


Final Answer:

First normal form (1NF)

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