Re: Relational Algebra Expression

On Feb 9, 4:47 pm, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> gamehack wrote:
> [snip]
> > What I'm trying to do is extract all the years where we have more than
> > 1 relation for the year. For the sample table, we need to get:
> > 1999
> > 2001
>
> > I tried to do in a couple of ways but I couldn't. I tried using a
> > projection on Year so that I can remove duplicates but then I can't
> > just use difference because the new relations are not compatible. Any
> > hints are greatly appreciated.
>
> Equijoin on year and inequality theta-join on name project on year.

Hi,

I can't really understand what this means - can you bracket it so I can see the results of each operation?

Thanks very much,
g Received on Sat Feb 09 2008 - 17:59:43 CET