How many Borough-type stores located in the city of Brooklyn have a population of less than 3 million?
"Brooklyn" is the CityName; population of less than 3 million refers to Population < 3000000
SELECT SUM(CASE WHEN Population < 3000000 AND Type = 'Borough' AND `City Name` = 'Brooklyn' THEN 1 ELSE 0 END) FROM `Store Locations`