Identify Repeat Advertisers from Consecutive Weeks

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 Technical Screen 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

SUBMISSIONS

+--------------+-----------+-----------+
| advertiser_id| ad_id     | week_id   |
+--------------+-----------+-----------+
| A123         | 9001      | 1         |
| A123         | 9005      | 2         |
| B456         | 9010      | 1         |
| C789         | 9020      | 2         |
| B456         | 9012      | 2         |
+--------------+-----------+-----------+

##### Scenario

Company holds weekly advertiser submissions log and wants to know repeat advertisers across two consecutive weeks.

##### Question

Write an SQL query that returns the advertiser_id(s) that submitted ads in BOTH Week 1 and Week 2.

##### Hints

Filter by week_id, use INTERSECT, self-join, or GROUP BY HAVING COUNT(DISTINCT week_id)=2.

PracHub · Accepted Answer

This question evaluates a candidate's proficiency in manipulating relational data to identify recurring entities across consecutive time periods, focusing on SQL/Python data manipulation and temporal comparison of records.

Quick Overview

Identify Repeat Advertisers from Consecutive Weeks