Reactivated Users
ASKED IN INTERVIEWMeta
Problem Statement
Find users active in Feb 2026 who were inactive in Jan 2026 but active at some point before Jan 2026.
Rules:
- Output columns: user_id.
- Current: 2026-02.
- Previous: 2026-01.
- Sort by user_id ASC.
Tests your understanding of
Set Theory, Filtering, Date Manipulation and EXCEPT
Input Tables
user_activity
| user_id(INTEGER) | activity_date(DATE) |
|---|---|
| 1 | 2025-12-15 |
| 1 | 2026-02-01 |
| 2 | 2026-01-10 |
| 2 | 2026-02-05 |
| 3 | 2026-02-10 |
| 4 | 2025-11-01 |
| 4 | 2026-02-20 |
users
| user_id(INTEGER) | signup_date(DATE) |
|---|---|
| 1 | 2025-01-01 |
activity_types
| activity_id(INTEGER) | activity_name(VARCHAR) |
|---|---|
| 1 | Login |
Expected Output
| user_id(INTEGER) |
|---|
| 1 |
| 4 |
Tags
HardASKED IN INTERVIEWSet TheoryFilteringDate ManipulationEXCEPT
25-35 min
36%