Can SQL calculate aggregate functions across multiple tables?

Question

Let\'s say I have two existing tables, \"dogs\" and \"cats\":

 dog_name | owner
 ---------+------
 Sparky   | Bob
 Rover    | Bob
 Snoopy   | Chuck
 Odie             


        

Answer 1

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