[questa risposta è basata su quella di Gordon]
Ho cambiato arr_time e dep_time in TIME tipi di dati, che semplificano i calcoli. Sono state inoltre aggiunte colonne dei risultati per total_time e wait_time. Nota :se ci sono dei loop possibili nel grafico, dovrai evitarli (possibilmente usando un array per memorizzare il percorso)
WITH RECURSIVE segs AS (
SELECT f0.flight_num::text as flight
, src_city, dest_city
, dep_time AS departure
, arr_time AS arrival
, airfare, mileage
, 1 as hops
, (arr_time - dep_time)::interval AS total_time
, '00:00'::interval as waiting_time
FROM flight f0
WHERE src_city = 'SLC' -- <SRC_CITY>
UNION ALL
SELECT s.flight || '-->' || f1.flight_num::text as flight
, s.src_city, f1.dest_city
, s.departure AS departure
, f1.arr_time AS arrival
, s.airfare + f1.airfare as airfare
, s.mileage + f1.mileage as mileage
, s.hops + 1 AS hops
, s.total_time + (f1.arr_time - f1.dep_time)::interval AS total_time
, s.waiting_time + (f1.dep_time - s.arrival)::interval AS waiting_time
FROM segs s
JOIN flight f1
ON f1.src_city = s.dest_city
AND f1.dep_time > s.arrival -- you can't leave until you are there
)
SELECT *
FROM segs
WHERE dest_city = 'LA' -- <DEST_CITY>
ORDER BY airfare desc
;
A proposito:le modifiche alla struttura della tabella:
create table flight
( flight_num BIGSERIAL PRIMARY KEY
, src_city varchar
, dest_city varchar
, dep_time TIME
, arr_time TIME
, airfare INTEGER
, mileage INTEGER
);
E ai dati:
insert into flight VALUES
(101, 'Montreal', 'NY', '05:30', '06:45', 180, 170),
(102, 'Montreal', 'Washington', '01:00', '02:35', 100, 180),
(103, 'NY', 'Chicago', '08:00', '10:00', 150, 300),
(105, 'Washington', 'KansasCity', '06:00', '08:45', 200, 600),
(106, 'Washington', 'NY', '12:00', '13:30', 50, 80),
(107, 'Chicago', 'SLC', '11:00', '14:30', 220, 750),
(110, 'KansasCity', 'Denver', '14:00', '15:25', 180, 300),
(111, 'KansasCity', 'SLC', '13:00', '15:30', 200, 500),
(112, 'SLC', 'SanFran', '18:00', '19:30', 85, 210),
(113, 'SLC', 'LA', '17:30', '19:00', 185, 230),
(115, 'Denver', 'SLC', '15:00', '16:00', 75, 300),
(116, 'SanFran', 'LA', '22:00', '22:30', 50, 75),
(118, 'LA', 'Seattle', '20:00', '21:00', 150, 450);
