# CHECK Constraint

A constraint requiring inserted or updated rows to satisfy a search condition.

## What does **CHECK Constraint** do in a relational database?

**CHECK Constraint** — A constraint requiring inserted or updated rows to satisfy a search condition.

```sql
CREATE TABLE customer (
    customer_id INTEGER PRIMARY KEY,
    email CHARACTER VARYING(255) NOT NULL,
    status CHARACTER VARYING(20) DEFAULT 'active'
);
```

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

Updated: September 27, 2026

Source: https://www.ask-codey.com/glossary/check-constraint