How many businesses in the city of Scottsdale open on Sunday at 12PM?
businesses that opened on Sunday refers to day_of_week = 'Sunday'; businesses that opened at 12PM refers to opening_time = '12PM'
SELECT COUNT(DISTINCT T2.business_id) FROM Business AS T1 INNER JOIN Business_hours AS T2 ON T1.business_id = T2.business_id INNER JOIN Days AS T3 ON T2.day_id = T3.day_id WHERE T1.city = 'Scottsdale' AND T3.day_of_week = 'Sunday' AND T2.opening_time = '12PM'