Which statement correctly describes First Normal Form (1NF)?

Which statement correctly describes First Normal Form (1NF)?

• A. Each column holds a single piece of data within an entity.
• B. Tables must contain only one row.
• C. All data must be unique.
• D. Data types must be identical across a column.

Answer: (A)

Atomicity of values in a table is what 1NF enforces. In First Normal Form, every column value must be atomic—no repeating groups or multi-valued cells. This means each field contains a single value rather than a list or set of values. If you had a single cell with multiple phone numbers, that would violate 1NF; you’d split it so each cell holds one value, often placing each value in its own row or in separate columns as appropriate. A table can have many rows, and 1NF is about the content of each cell, not the total number of rows. The requirement that all data be unique isn’t part of 1NF; duplicates can exist and are typically addressed with keys. While a column is defined by a data type, that aspect is a schema rule, not the defining feature of 1NF—the key idea is that each cell holds a single, indivisible value.

Atomicity of values in a table is what 1NF enforces. In First Normal Form, every column value must be atomic—no repeating groups or multi-valued cells. This means each field contains a single value rather than a list or set of values. If you had a single cell with multiple phone numbers, that would violate 1NF; you’d split it so each cell holds one value, often placing each value in its own row or in separate columns as appropriate. A table can have many rows, and 1NF is about the content of each cell, not the total number of rows. The requirement that all data be unique isn’t part of 1NF; duplicates can exist and are typically addressed with keys. While a column is defined by a data type, that aspect is a schema rule, not the defining feature of 1NF—the key idea is that each cell holds a single, indivisible value.