Any of the books by Chris Date are a good place to start, although some find him a bit strident. A lot of people rip on SQL, but knowing it well is extremely h

Any of the books by Chris Date are a good place to start, although some find him a bit strident. A lot of people rip on SQL, but knowing it well is extremely helpful. With all the NoSQL hype it's easy to overlook the stuff RDBMSs are very, very good at--but they're not good at everything. (With the caveat that PG's JSON stuff brings NoSQL into the SQL world.)