Facebook Data Scientist SQL面经+参考答案

感谢楼主分享！

serena2005 发表于 2018-10-3 03:30
2) Create atable that tracks the user last status every day.
SELECT A.DATE, B.USER_ID, B.STATUS
(S ...

This is to ensure there will be a record for each user even though the user didn't have any action on that day.

对于1 （3），好像可以更简单一点，再用一个collesce省去case when：
SELECT A.* 
FROM EVERYDAY_SATUS 
UNION 
( 
SELECT  
COALESCE(A.USER_ID, B.USER_ID) AS USER_ID 
,COALESCE (A.ACTION, B.STATUS) AS STATUS 
,CURDATE() AS DATE 
FROM 
TABLE_TODAY A 
FULL OUTER JOIN  
TABLE_EVERYDAY B 
WHERE A.USER_ID = B.USER_ID 
AND B.DATE= CURDATE()-1 
 
); 

bergkamp 发表于 2018-10-1 13:24
请问这个为什么要Join呢？ 直接Select target_id, Count(Content_id) where target_id is not NULL (或者ty ...

Yes I think yours is the best solution for the first question.

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谢谢楼主！

mark thanks!

Thanks for sharing