PostgreSQL and SQL Resources
PostgreSQL Server Programming
A good primer on working with PL/pgSQL, "untrusted languages", and C. Though I disagree with many parts of it, I do think it covers a decent amount of material and it is well-presented.
PostgreSQL 9.0 High Performance
A little dated but full of valuable information. The best "explaining explain" you will find anywhere, which makes this book worth the price alone.
A more thorough review of this book is coming down the pipeline. This book was the book that finally made me "get" SQL. I highly recommend this book to anyone looking to take their next step in SQL and database design thinking.
7 Databases in 7 Weeks
The first chapter deals with PostgreSQL's text searching capabilities and other interesting topics. The other chapters cover Riak, HBase, MongoDB, CouchDB, Neo4j, and Redis, which is a good mix of technologies for comparison and contrast. There is a reason this book is so highly recommended: it is well-written, accurate, and full of interesting tidbits you may have difficulty finding elsewhere.
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