Compute 7-Day Rolling Average of Unique Post Viewers

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Q: What difficulty level is this coding question?

This is a Medium difficulty Data Manipulation (SQL/Python) question, commonly asked during Onsite rounds at TikTok.

Q: What role is this question designed for?

This question is commonly asked for Data Scientist candidates at TikTok during technical interviews.

Question

POST_VIEWS

+---------+------------+---------+
| user_id | view_date  | post_id |
| 101     | 2023-08-01 | 10      |
| 102     | 2023-08-01 | 11      |
| 101     | 2023-08-02 | 10      |
| 103     | 2023-08-03 | 12      |
| 104     | 2023-08-03 | 10      |

​

POSTS

##### Scenario

A social-media analytics team has two tables: POST_VIEWS records every user’s daily post views, and POSTS stores post metadata including a free-text hashtags field.

##### Question

Write an SQL query to compute, for every post, the 7-day rolling average of daily unique viewers ordered by view_date. Given a search term (e.g. 'Apple'), return all post_id values whose hashtags column contains that term (case-insensitive). State the logical execution order of SQL clauses (e.g. FROM, WHERE, GROUP BY…) and explain why knowing this order matters when debugging or optimizing queries.

##### Hints

Use COUNT(DISTINCT user_id) over a 7-day RANGE window; apply ILIKE or LOWER(hashtags) LIKE '%apple%'.

PracHub · Accepted Answer

This question evaluates proficiency with SQL data manipulation, window functions for rolling aggregates, deduplication of user events, and text-filtering of metadata.

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