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I just finished Rob Conery's book "A curious moon". Very enjoyable, funny, interesting. So not your usual technical book, so much better in so many ways. I was hooked. PostgreSQL in a scifi story, I would sure love another one like this.
Learning SQL beyond simple SELECT/INSERT/UPDATE is the best approach. There are so many sql language constructs the most developers are unaware of. I really would recommend the curious moon book for some playful sql learning
Learning some #PostgreSQL (and brushing up on my SQL) with
's SQL In Orbit course. Pretty cool to analyze actual data from the Cassini mission.