# Nonclustered Index

A separate sorted lookup structure that points back to the rows.

## What is **Nonclustered Index**?

A **nonclustered index** is a separate sorted structure pointing back to the rows, like a book's index. A table can have many; each speeds up certain searches but slows writes a little.

```sql
CREATE NONCLUSTERED INDEX IX_Customers_Email ON dbo.Customers (Email);
```

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

Updated: September 27, 2026

Source: https://www.ask-codey.com/glossary/nonclustered-index