Training Guide: Programming in HTML5 with JavaScript and CSS3 Ebook

582 CHAPTER 16 Offline web applications

Lesson 1: Working with Web SQL

Web SQL is arguably one of the most powerful options available to you. It provides a full rela-

tional database that includes many of the features you’ve come to enjoy from the server-side

database offerings.

Most current implementations are built on SQLite, which is one of the most widely

used lightweight database engines. It’s an open-source solution with a vibrant community

backing it.

After this lesson, you will be able to:

■■Describe the use of Web SQL.

■■Implement transactions using Web SQL.

Estimated lesson time: 20 minutes

Considering the questionable longevity of Web SQL

Before starting with Web SQL, be aware that the World Wide Web Consortium (W3C) has

stated that Web SQL is no longer on its recommendation track. In 2010, the W3C Web

Applications Working Group announced that it does not intend to maintain the specification.

NOTE DISCONTINUED SUPPORT

For further details regarding the W3C’s decision to discontinue support of the Web SQL

specifications, please see its explanation at http://dev.w3.org/html5/webdatabase/.

What this means for Web SQL depends on the browser you’re targeting. Although the

specification is no longer being maintained, some browsers have continued their support.

(See Chapter 15 for a complete list.) Therefore, Web SQL might be a viable option if you’re

building specifically for a platform such as iOS for iPad or iPhone. Another common use is in

Google Chrome extensions. If you’re building a browser-agnostic application, consider one of

the other offline storage solutions.

If you do plan on developing with Web SQL, it might be a good idea to remember what

alternatives are available (such as IndexedDB) and what level of effort might be needed if

other browser vendors decide to move away from it in the future.

Creating and opening the database

In the following sections, examine the syntax used to create or open a database, start a trans-

action, and execute a SQL command. Most of these commands should look very familiar if

you’ve used other relational databases.