Re: Foreign key problem

"Jay Dee" <ais01479_at_aeneas.net> wrote in message news:pnhkg.65506$YI5.8141_at_tornado.ohiordc.rr.com...
> x wrote:
> > "Jay Dee" <ais01479_at_aeneas.net> wrote in message
> > news:svbkg.68231$P2.43250_at_tornado.ohiordc.rr.com...
> >
> >>Hmm. A _name_ /would/ be necessary to permit your example..
> >
> > I know. But it shouldn't be.
> >
> >>But what is the meaning of the overlapping constraints
> >>with different names?
>
> > Overlapping as in the example, or overlapping as identical ?

> As in the example.

>> tables(t1).
>> tables(t2).

>> columns(t1,c1).
>> columns(t1,c2).
>> columns(t1,c3).
>> columns(t1,c4).

>> columns(t2,c5).
>> columns(t2,c6).
>> columns(t2,c7).

>> foreign_keys(t1,c1,t2,c5).
>> foreign_keys(t1,c2,t2,c6).
>> foreign_keys(t1,c3,t2,c7).

>> foreign_keys(t1,c2,t2,c6). "Saying something more than once doesn't make
it more true."
>> foreign_keys(t1,c3,t2,c7). "Saying something more than once doesn't make
it more true."
>> foreign_keys(t1,c4,t2,c5).

> t1(1,2,3,4).
> t2(1,2,3).
> t2(4,2,3).

> I interpreted the 'foreign_keys(...)'
> stanzas to be some sort of expressions of some sort of super
> constraint in which two of three referring columns had the
> same referents. What are those expressions? I don't know.
> What are super constraints? I don't know.

Sorry, I cannot parse the above.

> Did you have any specific reason for re-specifying those?

F1:(c1,c2,c3) references (c5,c6,c7)
F2:(c2,c3,c4) references (c6,c7,c5)

>> foreign_keys(f1,t1,c1,t2,c5).
>> foreign_keys(f1,t1,c2,t2,c6).
>> foreign_keys(f1,t1,c3,t2,c7).

>> foreign_keys(f2,t1,c2,t2,c6). "Saying something more than once doesn't
make it more true."
>> foreign_keys(f2,t1,c3,t2,c7). "Saying something more than once doesn't
make it more true."
>> foreign_keys(f2,t1,c4,t2,c5).

vs.

>> foreign_keys(t1,c1,t2,c5).
>> foreign_keys(t1,c2,t2,c6).
>> foreign_keys(t1,c3,t2,c7).
>> foreign_keys(t1,c4,t2,c5).

c1=c4=c5
(c1,c2,c3,c4) references (c5,c6,c7,c5) Received on Fri Jun 16 2006 - 09:32:01 CEST