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Data & Analytics · Foundational

First Normal Form (1NF)

A table is in 1NF when every column holds atomic (single) values, there are no repeating groups, and each row is unique.

Definition

1NF removes multivalued columns and repeating column groups such as Phone1, Phone2 and Phone3, typically by moving them to a separate table. A primary key must identify each row.

Example

Replacing a Phones column containing '555-1234, 555-9876' with a separate CustomerPhones table.

Exam tip

Comma-separated lists in a column or numbered repeating columns signal a 1NF violation.

Related terms