Data Analysis Using SQL and Excel, 2nd Edition

CHAPTER 2 What’s in a Table? Getting Started with Data Exploration

The previous chapter introduced the SQL language from the perspective of data analysis. This chapter uses SQL for exploring data, the first step in any analysis project. The emphasis shifts away from databases in general. Understanding what the data represents—and the underlying customers—is a theme common to this chapter and the rest of the book.

The most common data analysis tool, by far, is the spreadsheet, particularly Microsoft Excel. Spreadsheets show data in a tabular format. They give users power over the data, with the ability to add columns and rows, to apply functions, to summarize, create charts, make pivot tables, and color and highlight and change fonts to get just the right look. This functionality and the what-you-see-is-what-you-get interface make spreadsheets a natural choice for analysis and presentation.

Spreadsheets, however, are less powerful than databases because they are designed for interactive use. The historical limits in Excel on the number of rows (once upon a time, a maximum of 65,535 rows) and the number of columns (once upon a time, a maximum of 255 columns) clearly limited the spreadsheets to smaller applications. Even without those limits, spreadsheet applications often run on a local machine and are best applied to single tables (workbooks). They are not designed for combining data stored in disparate formats. The power of users’ local machines can limit the performance of ...