SQL可以跨多个表计算聚合函数吗？

SQL可以跨多个表计算聚合函数吗？

select owner, sum(num_dogs), sum(num_cats) from  (select owner, 1 as num_dogs, 0 as num_cats from dogs   union   select owner, 0 as num_dogs, 1 as num_cats from cats)group by owner