Question

The table objects

id    name    is_animal
-----------------------
1     dog     1
2     cat     1
3     chair   0
4     rabbit  1

The query

(SELECT name AS animal_name FROM objects WHERE is_animal = 1)
UNION
(SELECT name AS object_name FROM objects WHERE is_animal = 0)

and the result

[animal_name] => dog
[animal_name] => cat
[animal_name] => rabbit
[animal_name] => chair    // expected: [object_name] => chair

I’ve already used AS in the second SELECT, why does it return animal_name instead of object_name?

Answer 1

with UNION :

(SELECT name AS animal_name,'' object_name FROM objects WHERE is_animal = 1)
UNION
(SELECT '' as animal_name, name AS object_name FROM objects WHERE is_animal = 0)

with case :

select case is_animal when 1 name else '' end as  animal_name,
       case is_animal when 0 name else '' end as  object_name
from objects