MySQL allows many interesting variations on standard SQL In some cases, these can be considered developer-friendly These can also considered to be hindrances to supporting multiple databases Your hosting service might provide different databases (for example, hub.org offers PHP with PostgreSQL) You may be interested in enhancing your portable, standard database development skills Potential customers of your software might have standardized software environments and required a different database. Prediction from Mark Driver of Gartner Consulting on Sept. 13, 2005: *PHP will become a mainstream enterprise tool.* ~Note~: Recent releases of MySQL show that it, too, is adopting more standard SQL -- so this presentation should help you port your MySQL application to MySQL, as well.