Can SQL calculate aggregate functions across multiple tables?

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

I prefer this one:

select owner
     , count(dog_name) dogs
     , count(cat_name) cats
  from cats FULL OUTER JOIN dogs ON (cats.owner = dogs.owner)

In T-SQL for SQL Server 2005 (replace the CTE with an inline subquery if not):

WITH ownership AS (
    SELECT owner, COUNT(dog_name) AS num_dogs, 0 AS num_cats -- counts all non-NULL dog_name
    FROM dogs
    GROUP BY owner

    UNION

    SELECT owner, 0 AS num_dogs, COUNT(cat_name) as num_cats -- counts all non-NULL cat_name
    FROM cats
    GROUP BY owner
)
SELECT ownership.owner
    ,SUM(ownership.num_dogs) AS num_dogs
    ,SUM(ownership.num_cats) as num_cats
FROM ownership
GROUP BY ownership.owner