To some degree, syntax is standard among all of the SQL DBMSs. There are many DBMSs available; the most popular are those published by Microsoft and Oracle (Microsoft actually publishes two popular SQL DBMS offerings).
Flash techies seem to prefer open-source systems. For one thing, Microsoft and Oracle products cost money, while open -source systems are obviously free. For another, there is freedom to extend and debug the product and a community of sharing that benefits all. As in choosing PHP, we hope to benefit from and contribute to this community.
In the open-source world, the favorite DBMS is currently MySQL, and that is what we use in this book. MySQL has begun to cost money, which may later affect its popularity. But cost issues are not the dominant ones; syntax is more important. Most of the syntax in this chapter could be universally applied to any SQL program. But where the syntax varies from application to application, MySQL syntax will be used.