Compare with the previous row in SQL
SQL interview exercise on Window Functions, difficulty 2 of 3. Solve it in the editor beside a worked example; the tests run the moment you do.
Return every row with the change in revenue from the previous day in the same region (today minus yesterday). The first day of each region has no previous day and shows NULL. Columns: day, region, revenue, change. 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. Progress is saved in your browser, and in your account if you sign in.