Glossary · Database

Primary Key

A column or set of columns that uniquely identifies each row in a database table.

A primary key is a constraint that uniquely identifies each record in a database table. It must contain unique values and cannot contain NULL values. A table can have only one primary key, which may consist of a single column (simple key) or multiple columns (composite key). Primary keys serve as the main reference point for a record and are used by foreign keys in other tables to establish relationships. Common primary key strategies include auto-incrementing integers, UUIDs (Universally Unique Identifiers), and natural keys (meaningful values like email or ISBN). The choice of primary key impacts performance, scalability, and data distribution.

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