Retrieve Top Five Ads by Conversions in 30 Days

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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 Meta.

Q: What role is this question designed for?

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

Question

ads

ad_id | advertiser_id | created_at

1     | 101           | 2024-06-01

2     | 102           | 2024-06-03

3     | 101           | 2024-06-10

​

ad_impressions

impression_id | ad_id | user_id | impression_date

1001          | 1     | 501     | 2024-06-15

1002          | 2     | 502     | 2024-06-15

1003          | 1     | 503     | 2024-06-16

1004          | 3     | 501     | 2024-06-17

1005          | 2     | 504     | 2024-06-18

​

ad_conversions

conversion_id | impression_id | revenue | conversion_date

2001          | 1001          | 5.00    | 2024-06-15

2002          | 1003          | 2.50    | 2024-06-16

2003          | 1005          | 7.00    | 2024-06-18

##### Scenario

Analyze advertising performance; return the top N ads by conversions in the last M days using three related tables.

##### Question

Write SQL to return the five ads with the highest number of conversions in the past 30 days. Output ad_id, advertiser_id, total_conversions, sorted by total_conversions DESC. Exclude ads with zero conversions and handle impressions that never converted.

##### Hints

LEFT JOIN impressions to conversions, filter on date range, GROUP BY ad_id.

PracHub · Accepted Answer

This question evaluates a candidate's competency in SQL data manipulation, specifically aggregating event data and applying time-window filters to produce ranked metrics.

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