Join multiple tables with different columns

gistfile1.sql

SELECT i.*, 
       n.title, 
       n.url, 
       'NULL' as description 
FROM items i JOIN news n ON n.item_id = i.id 
UNION ALL 
SELECT i.*, 
       j.title, 
       j.url, 
       'NULL' as description 
FROM items i JOIN jobs j ON j.item_id = i.id 
UNION ALL 
SELECT i.*, 
       'NULL' AS title, 
       'NULL' AS url, q.description 
FROM items i JOIN questions q ON q.item_id = i.id 
ORDER BY created_at DESC;