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2783. Flight Occupancy and Waitlist Analysis
Description
Table: Flights
+-------------+------+
| Column Name | Type |
+-------------+------+
| flight_id | int |
| capacity | int |
+-------------+------+
flight_id is the column with unique values for this table.
Each row of this table contains flight id and its capacity.
Table: Passengers
+--------------+------+ | Column Name | Type | +--------------+------+ | passenger_id | int | | flight_id | int | +--------------+------+ passenger_id is the column with unique values for this table. Each row of this table contains passenger id and flight id.
Passengers book tickets for flights in advance. If a passenger books a ticket for a flight and there are still empty seats available on the flight, the passenger ticket will be confirmed. However, the passenger will be on a waitlist if the flight is already at full capacity.
Write a solution to report the number of passengers who successfully booked a flight (got a seat) and the number of passengers who are on the waitlist for each flight.
Return the result table ordered by flight_id in ascending order.
The result format is in the following example.
Example 1:
Input: Flights table: +-----------+----------+ | flight_id | capacity | +-----------+----------+ | 1 | 2 | | 2 | 2 | | 3 | 1 | +-----------+----------+ Passengers table: +--------------+-----------+ | passenger_id | flight_id | +--------------+-----------+ | 101 | 1 | | 102 | 1 | | 103 | 1 | | 104 | 2 | | 105 | 2 | | 106 | 3 | | 107 | 3 | +--------------+-----------+ Output: +-----------+------------+--------------+ | flight_id | booked_cnt | waitlist_cnt | +-----------+------------+--------------+ | 1 | 2 | 1 | | 2 | 2 | 0 | | 3 | 1 | 1 | +-----------+------------+--------------+ Explanation: - Flight 1 has a capacity of 2. As there are 3 passengers who have booked tickets, only 2 passengers can get a seat. Therefore, 2 passengers are successfully booked, and 1 passenger is on the waitlist. - Flight 2 has a capacity of 2. Since there are exactly 2 passengers who booked tickets, everyone can secure a seat. As a result, 2 passengers successfully booked their seats and there are no passengers on the waitlist. - Flight 3 has a capacity of 1. As there are 2 passengers who have booked tickets, only 1 passenger can get a seat. Therefore, 1 passenger is successfully booked, and 1 passenger is on the waitlist.
Solutions
-
# Write your MySQL query statement below SELECT flight_id, LEAST(COUNT(passenger_id), capacity) AS booked_cnt, GREATEST(COUNT(passenger_id) - capacity, 0) AS waitlist_cnt FROM Flights LEFT JOIN Passengers USING (flight_id) GROUP BY 1 ORDER BY 1;