Summary: in this tutorial, you will learn how to use the SQL Server CREATE INDEX statement to create nonclustered indexes for tables.
Introduction to SQL Server non-clustered indexes #
A nonclustered index is a data structure that improves the speed of data retrieval from tables. Unlike a clustered index, a nonclustered index sorts and stores data separately from the data rows in the table. It is a copy of selected columns of data from a table with the links to the associated table.
Like a clustered index, a nonclustered index uses the B-tree structure to organize its data.
A table may have one or more nonclustered indexes and each non-clustered index may include one or more columns in a table.
The following picture illustrates the structure of a non-clustered index: