FB店面跪经

脸书电面：
问题1：FB一个新product准备上线，如何判断这个product是否受欢迎？
我答得不好，记得当时说的是看thumb up的数量。现在想应该是做AB test

问题2：you have a table where you have date, user_id, song_id and count. It shows at the end of each day how many times in her history a user has listened to a given song. You have to update this on a daily basis based on a second table that records in real time w

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tyle="font-size:15px">SELECT USERID, SONG, COUNT FROM DAILY WHERE DATE = NOW()) A
GROUP BY A.USERID, A.SONG

Thanks for sharing! It helps a lot

问题2我觉得应该这样做，大家看对吗？

Select * from
Summary
Union all
(Select date(now()) as date, user_id, song_id, sum(count) as count
from
(Select user_id, song_id, count(*) as count
From daily
Group by user_id, song_id) a
Union all
(select user_id, song_id, count from summary
where date=date(now())-interval ‘1 day’) b
Group by date, user_id, song_id) today