"To many people, PostgreSQL and MySQL seem like
similar, alternative databases. Both are quickly gaining
popularity. Based on the track records of older versions, there's a
lot of debate over the speed of PostgreSQL and the durability of
MySQL. But times have changed and each database has progressed. On
both counts, the two packages are the closest they've ever been, so
when deciding which to use in a Web application, a developer
doesn't always have a clear winner.
MySQL's claim to fame is that it provides a reasonable set of
features, such as built-in SQL functions, that follow the 80/20
rule: It has the 20 percent of SQL capabilities that are needed for
80 percent of database applications. Developers of simple
applications can live without the remaining features, such as
stored procedures and subqueries, or can work around them with
creative client-side programming.
PostgreSQL, on the other hand, provides more features than
MySQL. These include more SQL functions, server-side procedural
languages, and sophisticated methods for date manipulation.
PostgreSQL also offers object-relational capabilities and geometric
data types. If you're developing an application that has highly
complex business rules, PostgreSQL lets you handle business logic
on the database server."