# Data Type

A rule defining which values a column or expression may contain and which operations apply.

## What is **Data Type** in a relational database?

**Data Type** — A rule defining which values a column or expression may contain and which operations apply.

```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

## In other subjects

- [Data Type in C#](https://www.ask-codey.com/glossary/data-type-c-sharp)
- [Data Type in Java](https://www.ask-codey.com/glossary/data-type-java)

Source: https://www.ask-codey.com/glossary/data-type-database