Question

Let’s say I have two existing tables, ‘dogs’ and ‘cats’:

 dog_name | owner  ---------+------  Sparky   | Bob  Rover    | Bob  Snoopy   | Chuck  Odie     | Jon   cat_name | owner  ---------+------  Garfield | Jon  Muffy    | Sam  Stupid   | Bob 

How do I write a query with this output?

 owner | num_dogs | num_cats  ------+----------+---------  Bob   |     2    |    1  Chuck |     1    |    0  Sam   |     0    |    1  Jon   |     1    |    1 

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