578. Get Highest Answer Rate Question

https://leetcode.com/articles/get-highest-answer-rate-question/

SELECT question_id as survey_log
FROM
(
    SELECT question_id,
         SUM(case when action="answer" THEN 1 ELSE 0 END) as num_answer,
        SUM(case when action="show" THEN 1 ELSE 0 END) as num_show,    
    FROM survey_log
    GROUP BY question_id
) as tbl
ORDER BY (num_answer / num_show) DESC
LIMIT 1