# ON Clause

A join clause containing its match condition.

## What does **ON Clause** do in a relational database?

**ON Clause** — A join clause containing its match condition.

```sql
SELECT customer.email, purchase_order.order_id
FROM customer
INNER JOIN purchase_order
    ON purchase_order.customer_id = customer.customer_id;
```

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

Updated: September 27, 2026

Source: https://www.ask-codey.com/glossary/on-clause