How many streets with restaurants are there in the Northern California region?
SELECT COUNT(T1.city) FROM geographic AS T1 INNER JOIN location AS T2 ON T1.city = T2.city WHERE T1.region = 'northern california'
database name:db_id restaurant
geographic table geographic Cols: city dtype text, country dtype text, region dtype text, 
generalinfo table generalinfo Cols: id restaurant dtype integer, label dtype text, food type dtype text, city dtype text, review dtype real, 
location table location Cols: id restaurant dtype integer, street number dtype integer, street name dtype text, city dtype text, 
