Book Image

Amazon SimpleDB Developer Guide

Book Image

Amazon SimpleDB Developer Guide

Overview of this book

SimpleDB is a highly scalable, simple-to-use, and inexpensive database in the cloud from Amazon Web Services. But in order to use SimpleDB, you really have to change your mindset. This isn't a traditional relational database; in fact it's not relational at all. For developers who have experience working with relational databases, this may lead to misconceptions as to how SimpleDB works.This practical book aims to address your preconceptions on how SimpleDB will work for you. You will be quickly led through the differences between relational databases and SimpleDB, and the implications of using SimpleDB. Throughout this book, there is an emphasis on demonstrating key concepts with practical examples for Java, PHP, and Python developers.You will be introduced to this massively scalable schema-less key-value data store: what it is, how it works, and why it is such a game-changer. You will then explore the basic functionality offered by SimpleDB including querying, code samples, and a lot more. This book will help you deploy services outside the Amazon cloud and access them from any web host.You will see how SimpleDB gives you the freedom to focus on application development. As you work through this book you will be able to optimize the performance of your applications using parallel operations, caching with memcache, asynchronous operations, and more.
Table of Contents (16 chapters)
Amazon SimpleDB Developer Guide
Credits
Foreword
About the Authors
About the Reviewers
Preface

Storing numeric values


Attributes that store number values, which need to be sorted or compared, need to use the technique of zero padding so that they work correctly when using lexicographical comparison. If you store two number values 2 and 10, a normal lexicographical comparison will result in the value 2 being greater than 10. This is, of course, not exactly what you would expect to get when comparing these values as numbers.

Note

The solution is to store the number values with padding for the right number of digits.

We will store 2 as 02. Now a lexicographical comparison between 02 and 10 will return what you expect! In order to pad your data correctly, you need to know the limits of the number values that will be stored. If you know how large a number is to be stored, you can then pad each number that is being stored in your attributes with the right number of digits.

If you need to store negative numbers as attribute values and want to compare them, then storing them with just a zero...