Calculate the percentage of businesses with the category name food that are open from 7AM to 8PM in the businesses with the same time.
DIVIDE(COUNT(business_id where category_name = 'Food' and opening_time = '7AM' and closing_time = '8PM'), COUNT(business_id where opening_time = '7AM' and closing_time = '8PM')) as percentage;
SELECT CAST(SUM(CASE WHEN T3.category_name = 'Food' THEN 1 ELSE 0 END) AS REAL) * 100 / COUNT(T3.category_name) FROM Business_Categories AS T1 INNER JOIN Business AS T2 ON T1.business_id = T2.business_id INNER JOIN Categories AS T3 ON T1.category_id = T3.category_id