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Data & Analytics · Foundational

Column

A named attribute of a table with a defined data type that every row stores a value (or NULL) for; also called a field.

Definition

Columns define the structure of a table: their names, data types, nullability and constraints. In relational theory a column is an attribute whose allowed values form its domain. Columnar databases store each column's values together on disk to speed up analytic scans.

Example

The column OrderDate DATE NOT NULL stores the date each order was placed.

Exam tip

The number of columns in a table is its degree; don't confuse it with cardinality, which counts rows or distinct values.

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