Funso (Chichewa): Ndi misika ingati inalemba mitengo ya khobwe pa masiku oposa awiri osiyana? 
Question (English): How many markets recorded cowpeas prices on more than two different dates?
Table: commodity_prices (difficulty: hard)
SQL: SELECT COUNT(*) FROM (SELECT market FROM commodity_prices WHERE commodity = 'Cow peas' GROUP BY market HAVING COUNT(DISTINCT collection_date) > 2);
Result: [(21,)]