FB Technical Phone Round 1

10/10 initial technical phone interview. There was a HR screening before this.  Good luck to everyone who's recruiting!

SQL:

-- Q1: how many posts were reported yesterday for each report Reason?

-- Table: user_actions

-- ds(date, String) | user_id | post_id | action ('view','like','reaction','comment','report','reshare') | extra (extra reason for the action, e.g. 'love','spam','nudity')

-- Q2: introduce a new table: reviewer_removals, please ca

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e to validate.

• Given revenue decrease, how would you make recommendations? (doesn't have to be yes or no answer)
  
  
    
  • Short term vs. long term: how much does revenue drops? User experience vs. revenue. Short term revenue drop vs. long term brand perception and long term revenue gain.
      
  • If user distribution changed: find cause and tackle that unimaged users
    

第二题我觉得是这样的诶
Select
a.ds,
count(distinct b.post_id)/sum(case when a.action =‘view’ then 1 else 0 end) as spam_rate
from user_actions a
left join on reviewer_removals b
on a.post_id = b.post_id
group by a.ds

个人觉得不需要考虑join on date，因为 如果一个post今天被remove 不代表只有今天是spam， reviewer_removals可以看作一个metadata table， 这个table的ds只是一个action的timestamp而已

Janeevans 发表于 2018-10-14 06:34
这是我第一题的解法
select
  action,

求解：
个人想法，
action=‘report’ 在where的时候已经经过了一次过滤了，为啥还要加group by action?
我理解group by extra即可

jessica.xjs 发表于 2019-3-29 15:02
第二题我觉得是这样的诶
Select
a.ds,

求问sum里是不是会有重复的, 比如同一个post_id多个view, 在这里就做多次count，计数一共多少view？需不需要考虑去重呢？

楼主方便说这是啥职位么？偏产品？

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Chubbie 发表于 2018-10-12 11:26
楼主方便说这是啥职位么？偏产品？

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General Data Science/Analytics Intern :)

这是我第一题的解法
select
  action,
  extra
  count(distinct post_id)
from
  user_actions
where
  user_id is not null and
  action = 'report' and
  date(date) = date_sub(current_date, interval 1 day)

但是我没太明白第二个sql 题目的意思，追加的table 里面所有的post 都是被removed 了么？reviewer_id 是单独的一种id 还是可以match 到user_id? 一个post被removed 了是不是就等于confirm了这个post 是真正的有问题 （i.e. if this post is reported as spam and is removed, then it's an actual spam?）? 我应该会先把这些问题和面试官clarify 好了才开始做题吧。

补充内容 (2018-10-14 06:36):
sorry, SQL 少了group by 部分：
group by
  action,
  extra

Thanks for sharing

Janeevans 发表于 2018-10-14 06:34
这是我第一题的解法
select
  action,

Everything in reviewer_removals is removed.  Reviewers are FB employees, so reviewer_id doesn't matter.

谢谢楼主分享！ 想问下SQL题目两个table各个attribute是什么意思？

-- Table: user_actions
-- ds(date, String) | user_id | post_id | action ('view','like','reaction','comment','report','reshare') | extra (extra reason for the action, e.g. 'love','spam','nudity')
post_id 是user_id News Feed 里面的post么？ 换句话说不是这个user post的，是别人post的。action = view是怎么算的呢，需不需要用户点开才算view？
每个action都会有extra reason么，可不可以用户report某个post，但是不给reason？

-- Q2: introduce a new table: reviewer_removals, please calculate what percent of daily content that users view on FB is actually spam?
-- no need to consider if the removal happen at the same post date or not.
-- ds(date, String) | reviewer_id |post_id
不明白这个table和上个table的关系，比如user1 report post1 due to spam，然后post1被FB employee review，post1就会在第二个table里面么？还是post1被确认是spam以后才会在第二个table里？

多谢啦！

还想问一下楼主 AB test sample size n 是什么formula呀？ 我一般都用网上的calculator，只要输入 alpha， beta， 以及change就行了。谢谢啦！

product sense 题目这么多么…

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ooqq77 发表于 2018-10-18 15:21
product sense 题目这么多么…

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Yeah Haha. Cuz the SQL part lasted only 5-10 minutes. So the rest of the 40 minutes was all on product and basic stats questions.