# Clustered Index

The index that decides the order rows are stored in; one per table.

## What is **Clustered Index**?

A **clustered index** decides the order the table's rows are physically stored in. A table can have only one; by default it is the primary key.

```sql
CREATE CLUSTERED INDEX IX_Orders_PlacedAt ON dbo.Orders (PlacedAt);
```

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Updated: September 27, 2026

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