Among the working days from Monday to Saturday, which businesses with the category names work the most days?
days from Monday to Saturday refer to day_id between 2 and 7; work the most days can be computed as MAX(COUNT(category_name where day_id between 2 and 7));
SELECT T2.category_name FROM Business_Categories AS T1 INNER JOIN Categories AS T2 ON T1.category_id = T2.category_id INNER JOIN Business_Hours AS T3 ON T1.business_id = T3.business_id INNER JOIN Days AS T4 ON T3.day_id = T4.day_id GROUP BY T2.category_name ORDER BY COUNT(T3.day_id) DESC LIMIT 1