Евгений Быков

SELECT t1.id AS company_id,
       (SELECT COUNT(*)
            FROM table_two t2
            WHERE t2.campaign_id = t1.company_id
       ) AS count
      FROM table_one t1;

SELECT Id, Customer,
       (SELECT SUM(op.Weight) FROM Order_position op WHERE op.Order_id = o.Id),
       (SELECT SUM(oo.Price * oo.Value) FROM Order_other oo WHERE oo.Order_id = o.Id)
    FROM Order o
    WHERE Id = 1