I've only looked at the Java Blend documentation while assessing it's use in a project, but I'll tell you the little I know and I can't promise accuracy
and my opinion. Java Blend is a high level abstraction on top of
JDBC to do Object to relational database table mapping without having to write your own persistence layer. In other words, you don't have to know JDBC, or more importantly SQL, and all the really scary problems that come with object to relational mapping in writing your own persistence layer (transactions and atomicity, caching, locking, etc). Java Blend locks you into using specific databases on specific operating systems (Oracle on Solaris/NT and one other I believe the last time I looked), and really is high level in nature. It will take your objects and even create tables or vice versa if I remember correctly. It will also be a product, and I would assume an expensive one.
Personally, unless you really need a full blown plastic wrap package and you don't have the time and/or experience to write a more customized persistence framework, it seemed to complex and proprietary to me. Of course, writing your own persistence framework is no easy task. There is quite a bit of documentation on Java Blend now on Sun's site, although you might have to dig a little bit to get to it. It reminds of a much more full featured version of what you get packaged with some app servers to handle persistent beans.
I really can't give you any advice on good SQL books... I've been doing SQL stuff long enough now that I generally can get away with web references...
But, in a very related vein, I can give my opinion as far as JDBC books - which do have a small amount of SQL as required in them, and could help you with using SQL in the Java realm. For my top choice, I like "JDBC(TM) API Tutorial and Reference, Second Edition: Universal Data Access for the Java(TM) 2 Platform (Java Series)" as a good basic tutorial and reference... definitely the best reference.
Although the title is a little deceptive, I like "Database Programming With Jdbc and Java (O'Reilly)" by George Reese - this book is more of a tutorial on how to build a persistence framework in a distributed environment than a book on JDBC. The only problem with it, other than the title, is that it is showing its' age (1997). I emailed the author about 6 months ago and he said that a new edition would be out soon.
Anyway, have fun in your adventures!
