What intrigued me about "Trees in SQL" was "This model is a natural way to show
a parts explosion....."---a "Bill of Materials".
I was saving the article for future reference. Thanks for the clear
explanation, Bill.
RRR
Ben Petersen wrote:
>
> Bill,
>
> Thanks for turning the lights on. Taking a moment to look at them
> as two separate sets of data made all the difference. You'ld think
> by now I wouldn't get stuck in that mire.
>
> Ben Petersen
>
> On 24 Aug 2001, at 22:23, Bill Downall wrote:
>
> > Don't think of p1 and p2 as the "same" table. They are two separate
> > and distinct instances of empl. They are linked in the conditions, but
> > they are just like two totally separate tables with identical sets.
> >
> > The first example says that p1 is the table of employees named 'fred',
> > and p2 is employees with an lft greater than or equal to fred's lft, and
> > less than or equal to fred's rgt.
> >
> > That's different from example two, where logically, p2 is a query of
> > employees named fred, and p1 is a query of employees with an lft
> > LESS THAN or equal to Fred's lft and also GREATER THAN or equal
> > to fred's rgt.
> >
> > Bill
> >
> > On Fri, 24 Aug 2001 19:57:20 +0100, Ben Petersen wrote:
> >
> > >They are correct, but I don't get it, as p1 and p2 are the same
> > >table, and the only difference in the queries is
> >
> >
> >
> >
