Provide the businesses name in Tempe city whose opening hours are earlier than 8AM.
opening hours refers to opening_time; earlier than 8AM refers to opening_time < '8AM';
SELECT T1.category_name FROM Categories AS T1 INNER JOIN Business_Categories AS T2 ON T1.category_id = T2.category_id INNER JOIN Business AS T3 ON T2.business_id = T3.business_id INNER JOIN Business_Hours AS T4 ON T3.business_id = T4.business_id WHERE T3.city LIKE 'Tempe' AND T4.opening_time < '8AM'