Re: Aggregation is Inverse of Join

On Jan 15, 8:41 am, "Walt" <wami..._at_verizon.net> wrote:
> "Marshall" <marshall.spi..._at_gmail.com> wrote in
>
> > Well, I've run out of steam. More later.
>
> > Marshall
>
> > PS. I told you I wasn't organized.

> Interesting. It's going to take me weeks to get it.
>
> In the meantime, what is the inverse of Project?

I think the usual term is "extend."

In the relational lattice, project is just a specialization of the inner union, with one of the operands having cardinality zero.

Marshall Received on Mon Jan 15 2007 - 13:15:30 CST