Give the street number of a bar in Oakland with a 2.7 review.
street number refers to street_num; bar refers to food_type = 'bar'; Oakland refers to city = 'oakland'; 2.7 review refers to review = 2.7
SELECT T2.street_num FROM generalinfo AS T1 INNER JOIN location AS T2 ON T1.id_restaurant = T2.id_restaurant WHERE T1.review = 2.7 AND T2.city = 'oakland' AND T1.food_type = 'bar'