Subqueries with NOT EXISTS

NOT EXISTS works like EXISTS, except the WHERE clause in which it is used is satisfied if no rows are returned by the subquery.

For example, to find the names of products that are not in the wheels subcategory:

USE AdventureWorks2008R2;
GO
SELECT Name
FROM Production.Product
WHERE NOT EXISTS
    (SELECT * 
     FROM Production.ProductSubcategory
     WHERE ProductSubcategoryID = 
            Production.Product.ProductSubcategoryID
        AND Name = 'Wheels')