Identify Duplicate Posts by User and Date

Q: How do I practice SQL interview questions?

PracHub provides an interactive SQL console where you can write and test queries against real database schemas. Get instant feedback and compare your solution with the expected output.

Q: What difficulty level is this coding question?

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

Q: What role is this question designed for?

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

Question

posts

+---------+---------+---------------------+---------------+
| post_id | user_id | created_at          | content       |
+---------+---------+---------------------+---------------+
| 101     | 1       | 2024-05-01 10:00:00 | hello world   |
| 102     | 1       | 2024-05-01 10:00:00 | hello world   |
| 103     | 2       | 2024-05-02 12:00:00 | good morning  |
| 104     | 1       | 2024-05-03 09:00:00 | hello world   |
| 105     | 2       | 2024-05-02 12:05:00 | good morning  |
+---------+---------+---------------------+---------------+

##### Scenario

Meta wants to detect duplicate posts so they can surface only unique content in users’ feeds.

##### Question

Given table posts(post_id, user_id, created_at, content), write SQL that returns user_id, content, duplicate_count for posts where the same user posted identical content on the same calendar day (duplicate_count ≥
2).

##### Hints

Group by user_id, content, DATE(created_at); HAVING COUNT(*) > 1.

PracHub · Accepted Answer

This question evaluates a candidate's competency in data manipulation and deduplication, focusing on aggregation and handling of temporal attributes to identify repeated entries by the same user.

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