Moving average with a frame in SQL
SQL interview exercise on Window Functions, difficulty 3 of 3. Solve it in the editor beside a worked example, or cold in Interview mode with the example hidden; the tests run the moment you do.
Return a 3-day moving average of revenue per region: the average of the current day and the two days before it (fewer at the start), rounded to 1 decimal. Columns: day, region, moving_avg. Sorted by region, then day.
Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Interview mode hides the example: solve it from memory, without the hint or the solution, and it counts as solved cold. Progress is saved in your browser, and in your account if you sign in.