Запрос SQL:SELECT a, b, SUM(c) FROM vtableGROUP BY (a,b);
Выборку, эквивалентную результату запроса, возвращает команда:
(Отметьте один правильный вариант ответа.)
Варианты ответа
SELECT a, b, SUM(c) FROM vtable GROUP BY a, b UNION ALL SELECT a, NULL, SUM(c) FROM vtable GROUP BY a UNION ALL SELECT NULL, b, SUM(c) FROM vtable GROUP BY b UNION ALL SELECT NULL, NULL, SUM(c) FROM vtable;
SELECT a, b, SUM(c) FROM vtable GROUP BY a, b UNION ALL SELECT a, NULL, SUM(c) FROM vtable GROUP BY a UNION ALL SELECT NULL, NULL, SUM(c) FROM vtable;
SELECT a, NULL, SUM(c) FROM vtable GROUP BY a UNION ALL SELECT NULL, b, SUM(c) FROM vtable GROUP BY b; UNION ALL SELECT NULL, NULL, SUM(c) FROM vtable;
SELECT a, NULL, SUM(c) FROM vtable GROUP BY a UNION ALL SELECT NULL, b, SUM(c) FROM vtable GROUP BY b;(Верный ответ)