Задание: 30 (Serge I: 2003-02-14)
Вывод: point, date, суммарный расход пункта за день (out), суммарный приход пункта за день (inc).
Отсутствующие значения считать неопределенными (NULL).
select point, date, SUM(sum_out), SUM(sum_inc)
from( select point, date, SUM(inc) as sum_inc, null as sum_out from Income Group by point, date
Union
select point, date, null as sum_inc, SUM(out) as sum_out from Outcome Group by point, date ) as t
group by point, date order by point