> >> > -- c *= b *= a =* d =* f
> >> > select * from a, outer( b, outer c), outer (d, outer f )
> >> > where a.b_id = b.id and b.c_id = c.id and a.d_id = d.id and d.f_id = f.id;
> >>
> >> from a full join b on (a.id=b.id)
> >> full join c on (b.id=c.id)
> >> full join d
> >>
> >
> > I guess, you don't get it. Probably so
>
> I don't get it either. by *= do you mean the Oracle-style outer join?
> in which case why is this not just
>
> select * from a,
> left outer join b on (a.b_id = b.id)
> left outer join c on (b.c_id = c.id)
> left outer join d on (a.d_id = d.id)
> left outer join f on (d.f_id = f.id)
>
The equal expression would be like this:
select * from a
left outer join (b left outer join c on (b.c_id = c.id) ) on (a.b_id = b.id)
left outer join (d left outer join f on (d.f_id = f.id) ) on (a.d_id = d.id)
and that is a double length of original SQL and has not very clear syntax in my opinion.
Additionally it can be very funny if we try to append a join conditions like "c.iso = d.iso"
> You can parenthesize it different ways but I think the result in this
> case is actually the same.
>
I'm not sure.
> > select * from a left outer join b on (a.b_id=b.id) ....
> >
> > But I don't see any clear way to specify that table C should be outer joined only if we got a row from table B.
>
> Well that would be the default since if you get no row from b b.c_id
> will be null.
>
and if I have a row in table C where c.id is null? A don't know.
I found a good explanation about informix outer joins.
http://savage.net.au/SQL/outer-joins.html
Please take a look at that.
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