# Unique Key

One or more columns constrained so duplicate combinations are not allowed.

## What is **Unique Key** in a relational database?

**Unique Key** — One or more columns constrained so duplicate combinations are not allowed.

Level: Novice · [More Database terms at this level](https://www.ask-codey.com/glossary/subjects/database/novice)

Updated: September 27, 2026

Source: https://www.ask-codey.com/glossary/unique-key