And these are some links I've been looking at/considering:
http://www.amazon.com/Advanced-Oracle-SQL-Programming-Focus/...
http://www.amazon.com/Pro-Oracle-SQL-Karen-Morton/dp/1430232...
http://www.amazon.com/SQL-Antipatterns-Programming-Pragmatic...
http://www.amazon.com/Joe-Celkos-Smarties-Fourth-Edition/dp/...