Re: Relational Algebra and Aggregate Functions

Thanks for all the good replies (both on and off list). It seems the
consensus is for me to read Christopher Date. I found two relevant Date
books:
1) Introduction to Database Systems
http://www.amazon.com/Introduction-Database-Systems-Kannan-Swamynathan/dp/B001BVYKY4/ref=sr_1_5?ie=UTF8&s=books&qid=1248742811&sr=1-5
and
2) Database in Depth: Relational Theory for Practitioners
http://www.amazon.com/Database-Depth-Relational-Theory-Practitioners/dp/0596100124/ref=sr_1_7?ie=UTF8&s=books&qid=1248742811&sr=1-7
Any recommendations as to which? From the titles, I'd be inclined towards
the second, but not if the first is better. One thing I'm not interested in
is polemics against SQL and lamentations on how ignorant all practitioners
are.

On Mon, Jul 27, 2009 at 2:45 PM, Jeff Davis <pgsql(at)j-davis(dot)com> wrote:

> On Sun, 2009-07-26 at 15:36 -0400, Robert James wrote:
> > I'm working on improving my background database theory, to aid in
> > practice. I've found learning relational algebra to be very helpful.
> > One thing which relational algebra doesn't cover is aggregate
> > functions. Can anyone recommend any papers or web pages which provide
> > some good theoretical background for aggregate functions?
>
> When it comes to relational theory, C.J. Date is a good author. "An
> Introduction To Database Systems" covers pretty much everything.
>
> There's a formal definition of a relational algebra (including
> SUMMARIZE, which is the authors' version of an aggregate operator)
> defined with only two operators here:
> http://thethirdmanifesto.com/
> (look for "Appendix A")
>
> Although Appendix A is not easy to understand without some basic
> familiarity with the authors' other works.
>
> Regards,
> Jeff Davis
>
>