# For each ad impression, show the first campaign that user ever interacted with

Canonical URL: <https://datadriven.io/problems/for-each-ad-impression-show-the-first-campaign-that-user-ev-1249cf44>

Domain: SQL · Difficulty: medium

## Problem

For each ad impression, show the first campaign that user ever interacted with. Return user_id, ad_campaign, impression_time, and the result as first_campaign.

## Related

- [All practice problems](https://datadriven.io/problems)
- [Mock interview mode](https://datadriven.io/interview/for-each-ad-impression-show-the-first-campaign-that-user-ev-1249cf44)
- [SQL Interview Questions](https://datadriven.io/sql-interview-questions)
- [Data Engineering Interview Prep Guide](https://datadriven.io/data-engineer-interview-prep)
- [Daily Challenge](https://datadriven.io/daily)

---

Source: DataDriven (https://datadriven.io). 100% free data engineering interview prep. Live code execution against Postgres 16, Python 3.11, and Spark sandboxes. No paywall, no premium tier, no signup gate.