Book Image

Data Analysis Using SQL and Excel - Second Edition

By : Gordon S. S. Linoff
Book Image

Data Analysis Using SQL and Excel - Second Edition

By: Gordon S. S. Linoff

Overview of this book

Data Analysis Using SQL and Excel, 2nd Edition shows you how to leverage the two most popular tools for data query and analysis—SQL and Excel—to perform sophisticated data analysis without the need for complex and expensive data mining tools. Written by a leading expert on business data mining, this book shows you how to extract useful business information from relational databases. You'll learn the fundamental techniques before moving into the "where" and "why" of each analysis, and then learn how to design and perform these analyses using SQL and Excel. Examples include SQL and Excel code, and the appendix shows how non-standard constructs are implemented in other major databases, including Oracle and IBM DB2/UDB. The companion website includes datasets and Excel spreadsheets, and the book provides hints, warnings, and technical asides to help you every step of the way. Data Analysis Using SQL and Excel, 2nd Edition shows you how to perform a wide range of sophisticated analyses using these simple tools, sparing you the significant expense of proprietary data mining tools like SAS.
Table of Contents (18 chapters)
Free Chapter
1
Foreword
17
EULA

Query Engines and Performance

A SQL query describes the result set but does not specify the particular steps or algorithms used for generating the results. This allows the SQL optimizer to produce the best query plan—at least in theory.

By contrast, most computer languages are procedural. A command that says “sort the data” generally implements a particular algorithm for the sort—bubble sort, merge sort, quicksort, or perhaps some fancy parallel out-of-memory sort. The SQL statement ORDER BY simply says that the result set will be in a particular order. The statement does not specify exactly how that should be done. And, different databases take different approaches. For instance, in SQL Server, if the statement accesses only a single table and the ORDER BY key is the clustered index for the table, then an additional sorting step is generally unnecessary.

This section starts by introducing “order notation” from computer science as a way of characterizing...