member_activity has one row per user and active month (user_id, activity_month), where activity_month is the first day of the month ('YYYY-MM-01'); duplicates are possible. A reactivation is a month in which the user is active, the user was NOT active in the immediately preceding calendar month, and the user was active in some earlier month (a user's first active month is not a reactivation). Return every reactivation. Output columns: user_id, reactivation_month. Order by user_id, then reactivation_month.
| Column | Type |
|---|---|
| user_id | INTEGER |
| activity_month | DATE |
| user_id | activity_month |
|---|---|
| 1 | 2026-01-01 |
| 1 | 2026-03-01 |
| 2 | 2026-01-01 |
| 2 | 2026-02-01 |
| 3 | 2026-03-01 |
| user_id | reactivation_month |
|---|---|
| 1 | 2026-03-01 |
Solve it in the live editor on this page — run on sample data, then submit against hidden tests.
{{ totalCount }} questions in the style asked at Amazon, Microsoft, Google, Meta, Flipkart and more — {{ hardPct }}% Hard. Write SQL in a real database engine in your browser, run it on sample data, then evaluate against hidden tests.
Company tags show where this type of question is commonly reported in interviews. Questions, data and solutions are written by TechTown.
{{ cur.statement }}
No submissions yet. Press Evaluate to submit your query.
{{ solutionSql }}
{{ out.error }}
You have solved your 3 free questions — nice work! Log in (free) to unlock all 150 questions, keep your streak and appear on the leaderboard.