The first edition of this book set out to explain data analysis from an eminently
practical perspective, using the familiar tools of SQL and Excel. The guiding
principle of the book was to start with questions and guide the reader through
the solutions, both from a business perspective and a technical perspective.
This approach proved to be quite successful.
Much has changed in the ten years since I started writing the first edition.
The tools themselves have changed. In those days, Excel did not have a Ribbon,
for instance. And, window functions were rare in databases. The world that
analysts inhabit has also changed, with tools such as Python and R and NoSQL
databases becoming more common. However, relational databases are still in
widespread use, and SQL is, if anything, even more relevant today as technology
spreads through businesses big and small. Excel still seems to be the reporting
and presentation tool of choice for many business users. Big data is no longer
a future frontier; it is a problem, a challenge, and an opportunity that we face
on a daily basis.
The second edition has been revised and updated to reflect the changes in
the underlying software, with more examples and more techniques, and an
additional chapter on database performance. In doing so, I have strived to keep
the strengths from the first edition. The book is still organized around the
principles of data, analysis, and presentation—three capabilities that are rarely
treated together. Examples are organized around questions, with a discussion
of both the business relevance and the technical approaches to the problems.
The examples carry through to actual code. The data, the code, and the Excel
examples are all available on the companion website.