Question

I’m trying to learn nested queries in mysql and I’m stuck while selecting all hotels
which are 30 miles away from the city and have rooms that cost 150$

I can chose the rooms which are 30 miles away from the city and costs 150 with this query,but can’t reach the hotels.

    (select id from Rooms where cost = 150 and id in 
(select r_id from has_rooms where name IN (select name from is_at where l_town in 
(select town from Location where distance_from_city = 30))));



Rooms
+----+------+---------+
| id | cost | type    |
+----+------+---------+
|  1 |  100 | kral    |
|  2 |    0 | kralice |
|  3 |  150 | padisah |
|  4 |  150 | hop     |
|  5 |  150 | boss    |
+----+------+---------+

has_rooms
+------+------+
| r_id | name |
+------+------+
|    1 | A    |
|    2 | B    |
|    3 | C    |
|    4 | A    |
|    3 | A    |
+------+------+

is_at
+------+----------+
| name | l_town   |
+------+----------+
| A    | istanbul |
| B    | izmir    |
| C    | kars     |
| D    | adana    |
+------+----------+


select * from Location;
+--------------------+----------+----------------+----------+
| distance_from_city | postcode | street         | town     |
+--------------------+----------+----------------+----------+
|                 30 |     NULL | KENNEDY Street | istanbul |
|                 35 |     NULL | NULL           | kars     |
|                 40 |     NULL | Tenesse        | izmir    |
|                 50 |     NULL | NULL           | adana    |
+--------------------+----------+----------------+----------+

Hotel

+------+--------+
| name | rating |
+------+--------+
| A    |      5 |
| B    |      5 |
| C    |      4 |
| D    |      1 |
+------+--------+

Answer 1

SELECT  h.*
FROM    hotel h
JOIN    is_at ia
ON      ia.name = h.name
JOIN    location l
ON      l.town = ia.town
WHERE   EXISTS
        (
        SELECT  NULL
        FROM    rooms r
        JOIN    has_rooms hr
        ON      hr.r_id = r.id
        WHERE   hr.name = h.name
                AND r.cost = 150
        )
        AND distance_from_city <= 30