Re: boolean datatype ... wtf?

On Sep 29, 9:46 am, paul c <toledobythe..._at_oohay.ac> wrote:
> On 29/09/2010 4:51 AM, Paul Mansour wrote:
> ...
>
>
>
> > What is the problem with a Boolean data type?
> > .
> > It is fundamental - so fundamental  that in TTM it is the only
> > required scalar data type:  “We require that at least one built-in
> > scalar type be supported : Namely, type “Boolean” (BOOLEAN in Tutorial
> > D”).
>
> > Date and Darwen go on to give the obvious reasons for this.
>
> > The fact that DEE and DUM may be interpreted as TRUE and FALSE is not
> > relevant.  The result of A=B or A>B is not a relation.
>
> Aren't A=B and A>B relations?

I was under the impression that they are not, even if A and B are relations. But I may have misintepreted C.J. Date on this.

In "Database in Depth" he writes:

"In Chapter 2, I mentioned the fact that the equality comparison operator "=" applies to every type. In partitular, therefore it applies to relation types.... Now I must immediatly explain that these opeartors are not relational operators as such -- that is they are not part of the relational algebra-- because their result is a truth value, not a relation." Received on Wed Sep 29 2010 - 16:13:02 CEST