# LEFT OUTER JOIN

A join returning every left row and matching right rows, using NULLs when no right match exists.

## What is **LEFT OUTER JOIN** in a relational database?

**LEFT OUTER JOIN** — A join returning every left row and matching right rows, using NULLs when no right match exists.

```sql
SELECT customer.email, purchase_order.order_id
FROM customer
LEFT OUTER 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/left-outer-join