The Structured Query Language (SQL) "is the standard language for relational database management systems." A programmer building an online database will undoubtedly need to be very familiar with SQL, and this site is an excellent starting point. People who have never heard of SQL can learn the basics, or more advanced users can refresh their memories. The essential commands and functions are introduced in a very straightforward manner. The focus is on tables: creating them, adding records to them, and deleting records from them. Once the user feels comfortable with this material, a link to the tutorial's sequel is given, which goes into intermediate and advanced topics in somewhat greater detail.