For people who looked at this wanting to get going with using database systems (as opposed to creating them), I'd recommend:
Learning SQL by Alan Beaulieu SQL Performance Explained by Markus Winand SQL Cookbook by Anthony Molinaro
For people who looked at this wanting to get going with using database systems (as opposed to creating them), I'd recommend:
The three of these will take you up to a pretty useful level of SQL knowledge/understanding. The first two are fairly easy reading to boot.