A back-end data store is necessary when you implement any kind of application that is expected to generate some useful dynamic output. The most common ways to store the application’s data are in Relational Database Management Systems (RDBMS), which are very powerful tools that can store and manage our data.
Much like the other ingredients, the database is not a part of AJAX, but it’s not likely that you’ll be able to build real web applications without a database to support them. In this book, we’ll present simple applications that don’t have impressive data needs, but still require a database nevertheless. For the examples in this book we chose MySQL, which is a very popular database among PHP developers. However, because the database functionality is very generic, you can port it to other database systems with very little effort.
To build an application that uses databases you need to know the basics of:
Creating database tables that can hold your data
Writing SQL queries...