# IS NULL Predicate

A predicate testing whether a value is NULL.

## What does **IS NULL Predicate** do in a relational database?

**IS NULL Predicate** — A predicate testing whether a value is NULL.

```sql
SELECT customer_id
FROM customer
WHERE phone_number IS NULL;
```

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/is-null-predicate