How much more votes for episode 1 than for episode 5?
more votes refers to SUBTRACT(SUM(votes when episode = 1), SUM(votes when episode = 5))
SELECT SUM(CASE WHEN T1.episode = 1 THEN T2.votes ELSE 0 END) - SUM(CASE WHEN T1.episode = 5 THEN T2.votes ELSE 0 END) AS diff FROM Episode AS T1 INNER JOIN Vote AS T2 ON T2.episode_id = T1.episode_id;