i have the following mysql database table designed,
ticket(id, code, cust_name);
passenger(id, ticket_id, name, age, gender, fare);
service(id, passenger_id, item, cost);
A ticket can have many passenger and each passenger can have multiple services purchased. What I want is to get the grand total of each ticket cost.
I have tried the following sql,
SELECT
SUM(fare) as total_fare,
(SELECT SUM(cost) as total_cost FROM services WHERE passenger.id = services.passenger_id) as total_service_cost
FROM
ticket
JOIN passenger ON passenger.ticket_id = ticket.id
Though, the result gets the total of passenger fare as total_fare but for the service cost, it sums and returns the first passenger's total service cost only.
I thinks i need some more nesting of queries, need help and if possible please how can i get the result as grand total summing up both passenger fare and service cost total.
OK here is the sql insert statment to clarify,
INSERT INTO `ticket` (`id`, `code`, `cust_name`) VALUES
(1, 'TK01', 'Dipendra Gurung');
INSERT INTO `passenger` (`id`, `ticket_id`, `name`, `age`, `gender`, `fare`) VALUES
(1, 1, 'John', '28', 'M', 120),
(2, 1, 'Kelly', '25', 'F', 120);
INSERT INTO `services` (`id`, `passenger_id`, `item`, `cost`) VALUES
(1, 1, 'S1', 30),
(2, 1, 'S2', 50),
(3, 2, 'S3', 50);
I want to get the total cost of the ticket 'TK01' (including total fare and services total). The sql must return total fare as 120+120 = 240 and total services as 30+50+50 = 130.
Thanks! :)
解决方案
First of all in your current table schema you have no way to distinguish between services that have been sold to the same passenger in different tickets. Therefore you have no way to correctly calculate total_cost per ticket. You have to have ticket_id in your service table.
Now, if you were to have a ticket_id in service table then a solution with a correlated subqueries might look like
SELECT t.*,
(SELECT SUM(fare)
FROM passenger
WHERE ticket_id = t.id) total_fare,
(SELECT SUM(cost)
FROM service
WHERE ticket_id = t.id) total_cost
FROM ticket t
or with JOINs
SELECT t.id,
p.fare total_fare,
s.cost total_cost
FROM ticket t LEFT JOIN
(
SELECT ticket_id, SUM(fare) fare
FROM passenger
GROUP BY ticket_id
) p
ON t.id = p.ticket_id LEFT JOIN
(
SELECT ticket_id, SUM(cost) cost
FROM service
GROUP BY ticket_id
) s
ON t.id = s.ticket_id
Note: Both queries take care of the fact that passenger can have multiple services per ticket or no services at all.
Now with your current schema
SELECT t.*,
(SELECT SUM(fare)
FROM passenger
WHERE ticket_id = t.id) total_fare,
(SELECT SUM(cost)
FROM service s JOIN passenger p
ON s.passenger_id = p.id
WHERE p.ticket_id = t.id) total_cost
FROM ticket t
and
SELECT t.id,
p.fare total_fare,
s.cost total_cost
FROM ticket t LEFT JOIN
(
SELECT ticket_id, SUM(fare) fare
FROM passenger
GROUP BY ticket_id
) p
ON t.id = p.ticket_id LEFT JOIN
(
SELECT p.ticket_id, SUM(cost) cost
FROM service s JOIN passenger p
ON s.passenger_id = p.id
GROUP BY p.ticket_id
) s
ON t.id = s.ticket_id
Just to get a grand total per ticket
SELECT t.*,
(SELECT SUM(fare)
FROM passenger
WHERE ticket_id = t.id) +
(SELECT SUM(cost)
FROM service s JOIN passenger p
ON s.passenger_id = p.id
WHERE p.ticket_id = t.id) grand_total
FROM ticket t
or
SELECT t.id,
p.fare + s.cost grand_total
FROM ticket t LEFT JOIN
(
SELECT ticket_id, SUM(fare) fare
FROM passenger
GROUP BY ticket_id
) p
ON t.id = p.ticket_id LEFT JOIN
(
SELECT p.ticket_id, SUM(cost) cost
FROM service s JOIN passenger p
ON s.passenger_id = p.id
GROUP BY p.ticket_id
) s
ON t.id = s.ticket_id