About 10 years ago, "Access Database Design & Programming" http://www.amazon.com/dp/0596002734 was my introduction to relational algebra, and "The Guru's Guide to Transact-SQL" http://www.amazon.com/dp/0201615762 filled in the details on queries required for each day's new minor emergency.

Today I'm looking for the best online CBT options (teamtreehouse or whatever), online courses, better books, and/or any other options I might not even have considered ([online] user groups/communities, tutorials included with database servers, etc.?)

I was promised "an upcoming blog post specially focusing on learning SQL" back when Zipfian Academry rounded up their "Practical Intro to Data Science" a month ago https://news.ycombinator.com/item?id=5508261 , but I'm out of time to wait. (If anyone has additional recommendations specifically for learning more about business intelligence and/or data warehousing I'd greatly appreciate those too!)

Thanks for your time, and keep up the good work!