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

Sorting


SimpleDB supports sorting your query results, but please keep in mind that all comparisons of attributes and values are done in the lexicographical fashion that we discussed in the previous chapter. All data that you intend to sort that is not a plain string, but is a date or a number or a Boolean, must be appropriately encoded when storing it and then decoded correctly on retrieval. You can sort data based on a single attribute or the item names, in either ascending or descending order. If you do not specify a sort order, the results are sorted in the ascending order by default. Sorting is done by specifying the keywords order by and either asc or desc in the expression.

SimpleDB provides the following guidelines that you must be aware of when sorting the data:

  • All sort operations are of course performed in lexicographical order

  • If you want to sort your results, you must provide the sort attribute in at least one of the predicates of the expression

  • You can apply sorting to expressions...