what are pivot tables for?
Many Excel users are not familiar with, or are intimidated by Pivot Tables, one of the most powerful features in Excel. This page describes elementary Pivot Tables. A pivot table is a great reporting tool that sorts and sums independent of the original data layout in the spreadsheet.
A common scenario where PIVOT can be useful is when you want to generate cross-tabulation reports to summarize data. For example, suppose you want to query the PurchaseOrderHeader table in the AdventureWorks2008R2 sample database to determine the number of purchase orders placed by certain employees.