Done

app/models/city.rb

@@ -1,6 +1,32 @@
+
 class City < ActiveRecord::Base
   has_many :neighborhoods
   has_many :listings, :through => :neighborhoods
+  has_many :reservations, :through => :listings
 
-end
+  # Returns all of the available apartments in a city, given the date range
+  def city_openings(start_date, end_date)
+    booked_listings = "select distinct(l.id) FROM cities c JOIN neighborhoods n on c.id = n.city_id JOIN listings l on n.id = l.neighborhood_id JOIN reservations r on l.id = r.listing_id WHERE r.checkin >= #{start_date} AND r.checkout <= #{end_date}"
+    Listing.find_by_sql("select l.id, l.title FROM cities c JOIN neighborhoods n on c.id = n.city_id JOIN listings l on n.id = l.neighborhood_id WHERE l.id NOT IN (#{booked_listings})")
+  end
+
+  # Returns city with highest ratio of reservations to listings
+  def self.highest_ratio_res_to_listings
+    query = "select aggregate.id, aggregate.name, aggregate.listing_num, count(r.id) as res_num, count(cast(r.id as decimal)) / cast(listing_num as decimal) as ratio from (select c.id, c.name, count(l.id) as listing_num from cities c
+            JOIN neighborhoods n on c.id = n.city_id
+            JOIN listings l on n.id = l.neighborhood_id
+            group by c.id, c.name) as aggregate
+            JOIN neighborhoods n on aggregate.id = n.city_id
+            JOIN listings l on n.id = l.neighborhood_id
+            JOIN reservations r on l.id = r.listing_id
+            group by aggregate.id, aggregate.name, aggregate.listing_num
+            ORDER BY ratio DESC LIMIT 1"
+    City.find_by_sql(query).first
+  end
 
+  # Returns city with most reservations
+  def self.most_res
+    City.find_by_sql("select c.id, c.name, COUNT(c.id) as num_res from cities c JOIN neighborhoods n on c.id = n.city_id JOIN listings l on n.id = l.neighborhood_id JOIN reservations r on l.id = r.listing_id group by c.id, c.name ORDER BY num_res DESC LIMIT 1").first
+  end
+
+end