# Scalar Subquery

A subquery required to return one column and no more than one row.

## What is **Scalar Subquery** in a relational database?

**Scalar Subquery** — A subquery required to return one column and no more than one row.

```sql
SELECT order_id
FROM purchase_order
WHERE total_amount > (
    SELECT AVG(total_amount)
    FROM purchase_order
);
```

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/scalar-subquery