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.

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

Level: Journeyman · More Database terms at this level

Updated September 27, 2026