Code RoomEvery date something happened
MediumPrep Room Coding #5119

Every date something happened

SQLAlgorithms & data structuresMid~11 min

Return every distinct date on which an order was either placed or refunded, as `activity_date`, earliest first. A date should appear once.

What a strong answer looks like

Say what the query is meant to return before you write it, and name the shape of the answer: how many rows, grouped by what. Then watch the NULLs and the duplicates, because that is where most of these are lost.

Run onlyA query runs as one statement, so there is nothing to step through. Run it and read the rows.

0:00 of about 11 min

Expected, in this order

activity_date
2026-01-04
2026-01-19
2026-01-21
2026-02-02
2026-02-28
2026-03-03

Your result

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