2c - παραλλαγή.txt

-- Eρώτημα 2c (Παραλλαγή)
SELECT COUNT(DISTINCT contract_code) AS number_of_contracts, insurance_category, EXTRACT (YEAR FROM end_date) AS expired_year
FROM contracts
WHERE (EXTRACT (YEAR FROM end_date)>=2016 AND EXTRACT (YEAR FROM end_date)<=2020) AND (EXTRACT (YEAR FROM start_date)<2016 OR EXTRACT (YEAR FROM start_date)>2020)
GROUP BY insurance_category,EXTRACT (YEAR FROM end_date)