Re: RA with MV attributes
Date: Wed, 17 Jan 2007 14:27:19 GMT
Message-ID: <bnqrh.674673$1T2.569295_at_pd7urf2no>
Bob Badour wrote:
> Jon Heggland wrote:
>
>> David wrote:
>>
>>> Example
>>>
>>> r1(Names,Cars)
>>> bill, car1,car2,car4
>>> john,fred car3
>>>
>>> r2(Cars,Colours)
>>> car1,car3,car4 red
>>> car2 green
>>>
>>> r1 |X| r2 (Names,Cars,Colours)
>>> bill car1,car4 red
>>> bill car2 green
>>> john,fred car3 red
>>> john,fred green
>>>
>>> [...]
>>> For example the
>>> last tuple of r1 |X| r2 above doesn’t imply that John and Fred
>>> don’t own any cars.
>>
>>
>>
>> So what exactly does that last tuple mean?
> > > And what would happen if we replaced (car1,car3,car4)<->(red) with > (car1,car3,car4)<->(red,blue) in r2 ? > ...
Just curious, what does the symbol <-> stand for here?
p Received on Wed Jan 17 2007 - 15:27:19 CET