Re: Aggregation is Inverse of Join

From: paul c <toledobythesea_at_oohay.ac>
Date: Mon, 15 Jan 2007 22:58:58 GMT
Message-ID: <SGTqh.658799$1T2.620722@pd7urf2no>

Marshall wrote:
> 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
>

Surely, it's join.

p Received on Mon Jan 15 2007 - 16:58:58 CST