Pivot Table
What's Pivot Table?
Below is a brief excerpt from Wikipedia:
In data processing, a pivot table is a data summarization tool found in data visualization programs such as spreadsheets or business intelligence software. Among other functions, a pivot table can automatically sort, count total or give the average of the data stored in one table or spreadsheet, displaying the results in a second table showing the summarized data. Pivot tables are also useful for quickly creating unweighted cross tabulations. The user sets up and changes the summary's structure by dragging and dropping fields graphically. This "rotation" or pivoting of the summary table gives the concept its name.
A pivot table is especially useful with large amounts of data. For example, a store owner might list monthly sales totals for a large number of merchandise items in an Excel spreadsheet. If the owner wanted to know which items sold better in a particular financial quarter, it would be very time-consuming for them to look through pages of figures to find the information. A pivot table would allow the owner to quickly reorganize the data and create a summary for each item for the quarter in question.
Examples
There are a lot of articles, tutorials, videos on Web to help people learn how to use pivot table.
Bill Jelen, Michael Alexander: Pivot Table Data Crunching
Use Excel Pivot Tables to Organize Data is a good example demonstrating how to use Excel Pivot Table to analyze some election data. On WebPivotTable Demo Page, there are some demos how to use WebPivotTable to analyze the same data set.
History
The concept of pivot table came from Lotus Software (called Lotus Development Corporation before its acquisition by IBM) with a revolutionary spreadsheet program called Lotus Improv at 1987. In 1988, Steve Jobs saw the program and immediately wanted it developed for his upcoming NeXT computer platform. The program was eventually shipped in 1991 for the NeXT platform. A version for Windows was introduced in 1993.
Microsoft eventually picked up on this concept in Excel 5 in 1994. Years later, with the release of Excel 97, Microsoft offered users an enhanced pivot table wizard and key improvements to pivot table functionality, such as the capability to add calculated fields. Microsoft introduced the pivot chart with Excel 2000, providing users a way to represent pivot tables graphically.
In addition to Lotus Improv and Microsoft Excel, competing software programs such as Apache OpenOffice Calc, LibreOffice, Quantrix and numberGo provide similar implementations. Google Docs initially allowed the creation of basic pivot tables. In May 2011, Google announced the roll-out of a natively hosted pivot table feature in the Google spreadsheets editor.
Pivot functionality can also be found in other data visualization tools, including BI (business intelligence) packages. Excel Pivot Tables include the feature to directly query an OLAP (Online analytical processing) server for retrieving data instead of getting the data from an Excel spreadsheet. A pivot table is a simple client of an OLAP server. Almost all major BI vendors, like IBM, Microsoft, Oracle, SAP, SAS, Pentaho, MicroStrategy, provide their own pivot client tools to query their OLAP servers.