# LEFT & RIGHT JOIN — MySQL

Source: https://www.geekswithgeeks.com/en/mysql/sql-left-right-join

> Keep unmatched rows from one side of the join.

## LEFT JOIN

`LEFT JOIN` keeps every row from the left table, filling unmatched right-side columns with `NULL`.

```sql
SELECT c.name, o.id AS order_id
FROM customers c
LEFT JOIN orders o ON o.customer_id = c.id;
```

Output:

```
name        | order_id
Asha Rao    | 1
Rahul Mehta | 2
Priya Nair  | NULL
```

## RIGHT JOIN

`RIGHT JOIN` is the mirror of `LEFT JOIN` — it keeps every row from the right table instead. Most people just swap table order and use `LEFT JOIN`.

## Finding unmatched rows

Add `WHERE o.id IS NULL` after a `LEFT JOIN` to find customers with **no** orders at all.