CodeIgniter, Order by number of rows in a separate joined table? - php

Question

I have 4 tables that link together...
Firstly the hotels table
hotel_id
town_id
hotel_name
Then the towns table:
town_id
region_id
town_name
Then the regions table:
region_id
country_id
region_name
Finally the countries table
country_id
country_name
What I need to do is list the towns in order of how many hotels there are within that town.
The reason I have included the regions table and the countries table is because, when displaying that town, I need to display the country it's from. This can only be obtained via the regions table..
Therefore using the active records in CodeIgniter I have done this so far:
$this->db->join('regions','towns.town_region_id = regions.region_id');
$this->db->join('countries','regions.region_country_id = countries.country_id');
$query = $this->db->get('towns');
foreach ($query->result() as $row) {
echo "<li>";
echo "$row->town_name, $row->country_name";
echo "</li>";
}
This outputs:
London, United Kingdom
Washington, United States
New York, United States
Moscow, Russia
etc, etc
Each one of these cities have hotels in them. All I need now is to order them by how many hotels there are in each town..
Any help would be much appreciated! Thanks.

Answer 1

$this->db->select('t.*,c.*,COUNT(h.hotel_id) AS nhotels');
$this->db->from('towns t');
$this->db->join('hotels h','h.town_id = t.town_id');
$this->db->join('regions r','t.town_region_id = r.region_id');
$this->db->join('countries c','r.region_country_id = c.country_id');
$this->db->group_by('t.town_id');
$this->db->order_by("nhotels",'DESC');
$query = $this->db->get();
which will produce the following query:
SELECT `t`.*, `c`.*, COUNT(h.hotel_id) AS nhotels
FROM (`towns` t)
JOIN `hotels` h
ON `h`.`town_id` = `t`.`town_id`
JOIN `regions` r
ON `t`.`town_region_id` = `r`.`region_id`
JOIN `countries` c
ON `r`.`region_country_id` = `c`.`country_id`
GROUP BY `t`.`town_id`
ORDER BY `nhotels` DESC

Answer 2

SELECT
hotels.town_id,
count(hotels.hotel_id) from hotels AS hotels_count,
towns.town_name
FROM
hotels,
LEFT JOIN
towns ON hotels.town_id = towns.town_id
GROUP BY hotels.town_id
ORDER BY hotels_count DESC;