-- 4. Identify most popular photo (and user who created it)

SELECT 
    username,
    photos.id,
    photos.image_url, 
    COUNT(*) AS total
FROM photos
INNER JOIN likes
    ON likes.photo_id = photos.id
INNER JOIN users
    ON photos.user_id = users.id
GROUP BY photos.id
ORDER BY total DESC
LIMIT 1;