Funso (Chichewa): Kodi ndi maboma angati omwe analemba mitengo ya chimanga pa masiku onse olembera mitengo?
Question (English): How many districts recorded maize prices on every available collection date?
Table: commodity_prices (difficulty: hard)
SQL: SELECT COUNT(*) FROM (SELECT district FROM commodity_prices WHERE commodity = 'Maize' GROUP BY district HAVING COUNT(DISTINCT collection_date) = (SELECT COUNT(DISTINCT collection_date) FROM commodity_prices WHERE commodity = 'Maize'));
Result: [(12,)]