Basic Relational Theory
When I got started with SQL Server (when Microsoft first picked it up), I had worked on several database systems and even written a couple. However, I had little formal "relational" theory education--not until I took an Extended Relational Analysis (ERA) course which helped make the job of designing efficient databases a lot easier. Frankly, I don't remember where this course was given or who gave it but it sure looks like the course being offered by Relational Systems Corporation. I highly recommend this course to anyone building a relational database. Knowing how to normalize a new database or denormalize an existing database is only a small part of the database implementation process. ERA teaches developers how to interview a customer to determine what data needs to be stored and how it should be laid out in a database like SQL Server. The course also talked about practical reality that suggests denormalization makes sense in some selected cases (so to speak). Based on the number of questions I'm seeing lately, I think more developers (especially those who play the role of DBA) need to take the time to pick up this skill.