> > select ...
> > from t1 inner join t4 on t1.x=t4.x,
> > t2 left outer join t1
> > on t2.y=t1.y and
> > (t1.start_date between t2.start_date and t1.start_date),
> > t3 left outer join t1 on t3.x=t1.x and t3.y = t1.y;
> Let's be honest, folks. This is almost unreadable. I think we will
> need some simpler way to access _outer_ in addition to the ANSI way.
Nonsense! Especially since this isn't quite SQL92. Here is an SQL92
query (I think ;) :
select a, b, c from (t1 left join t2 using (x)) as j1 (a, b) right join t3 on (j1.a = t3.y);
So you do a left join with t1 and t2, name the resulting intermediate
table and columns, and then do a right join of the result with t3. I
can't see other syntaxes being very much more obvious, particularly
wrt predicting the actual result. Just because a query looks simpler
doesn't necessarily mean that the syntax alway produces a more robust
query.
> I can't imagine how I would answer a question: "How do I do an ANSI
> outer join". It would need its own FAQ page.
Well, *you're* the one writing the book :))
- Thomas
--
Thomas Lockhart lockhart@alumni.caltech.edu
South Pasadena, California
