text: --------------------------------------------------------------------------------
  --Example #15: Retrieve the name of the heaviest and lightest male and female child
  --------------------------------------------------------------------------------
  select c.*
        , first_value(c.firstname) over (partition by c.gender 
                                         order by c.weight
                                         rows between unbounded preceding
                                                  and unbounded following) as lt_child
        , last_value(c.firstname) over (partition by c.gender 
                                        order by c.weight
                                        rows between unbounded preceding
                                                 and unbounded following) as hv_child
    from childstat c
  ;
  