CREATE TABLE tip (tip_id INT, business_id VARCHAR, text TEXT, user_id VARCHAR, likes INT, year INT, month VARCHAR)
CREATE TABLE neighborhood (id INT, business_id VARCHAR, neighborhood_name VARCHAR)
CREATE TABLE business (bid INT, business_id VARCHAR, name VARCHAR, full_address VARCHAR, city VARCHAR, latitude VARCHAR, longitude VARCHAR, review_count BIGINT, is_open TINYINT, rating FLOAT, state VARCHAR)
CREATE TABLE checkin (cid INT, business_id VARCHAR, count INT, day VARCHAR)
CREATE TABLE user (uid INT, user_id VARCHAR, name VARCHAR)
CREATE TABLE review (rid INT, business_id VARCHAR, user_id VARCHAR, rating FLOAT, text TEXT, year INT, month VARCHAR)
CREATE TABLE category (id INT, business_id VARCHAR, category_name VARCHAR)

which neighborhood has the most number of businesses in Madison
SELECT neighborhood.neighborhood_name FROM business, neighborhood WHERE business.city = 'Madison' AND neighborhood.business_id = business.business_id GROUP BY neighborhood.neighborhood_name ORDER BY COUNT(DISTINCT (business.name)) DESC LIMIT 1
SELECT "neighborhood"."neighborhood_name" FROM "business" JOIN "neighborhood" ON "business"."business_id" = "neighborhood"."business_id" WHERE "business"."city" = 'Madison' GROUP BY "neighborhood"."neighborhood_name" ORDER BY COUNT(DISTINCT "business"."name") DESC NULLS LAST LIMIT 1