Try this problem in the playground
The sample tables will be auto-loaded — write a query and run it instantly.
UNION vs UNION ALL
Combine sales from 2023 and 2024. Show the difference between UNION (dedup) and UNION ALL (keep all).
Setup & sample data
The playground will create these tables and populate them automatically when you click "Open Playground" above:
Solutions
Multiple approaches — try each and understand the trade-offs.