Re: AW: [HACKERS] correlated subquery

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> >
> > SELECT f1.firstname, f1.lastname, f1.age
> > FROM friends f1
> > WHERE age = (
> > SELECT MAX(age)
> > FROM friends f2
> > WHERE f1.state = f2.state
> > )
> > ORDER BY firstname, lastname
> >
> > It finds the oldest person in each state. HAVING can't do
> > that, right?
>
> Having can do that particular case: (e.g. Informix)
>
> SELECT f1.firstname, f1.lastname, f1.age
> FROM friends f1, friends f2
> WHERE f1.state = f2.state
> GROUP BY f2.state, f1.firstname, f1.lastname, f1.age, f1.state
> HAVING f1.age = max(f2.age)
> ORDER BY firstname, lastname;

Yikes, you are right, and it works on PostgreSQL too. I have added it
to my book. Can anyone suggest queries that _must_ have subqueries?
Seems table aliases can replace subqueries in most/all? cases?

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