USE Northwind --Inspect indexes on Customers table in Nortwind sp_helpindex customers --The Execution Plan shows a clustered index scan is used --the CustomerID gives the sort order SELECT * FROM customers --Here the City index is used, not PK_Customers clustered index SELECT customerid, city from customers ORDER BY city --Inspect the Execution Plan to see the PK_Customers index is used. SELECT companyname, contactname, city, country, phone FROM customers --Create a composite index to cover the next query DROP INDEX customers.contact GO --Create an index on the Contact table CREATE UNIQUE NONCLUSTERED INDEX Contact ON customers (city, companyname, contactname, country, phone) --Notice in query Execution Plan no sort required as index sorted by City SELECT companyname, contactname, city, country, phone FROM customers ORDER BY city --Now a sort is required as index not sorted by Country SELECT companyname, contactname, city, country, phone FROM customers ORDER BY country