我有这样的表格结构 Table Structure
在这里，我想从bus_routines表中选择总线详细信息和avaliable_seat的所有数据，该数据是从buses.number_of_seat - reserved_seats.number_of_reserved_seat - booking.number_of_seat计算的，即使{{1}中没有数据} table和booking表，其中 bus_routines.sector_from = Ktm，bus_routines.sector_to = Pkr和bus_routines.date = 2015-12-15
它们之间的关系是：
bus和bus_routines - ＆gt;一对多的bus_routines和预订 - ＆gt; 一对多的bus_routines和reserved_seats - ＆gt;一对多
我尝试了以下查询
reserved_seats我得到了我想要的结果，但SELECT r.* , b.* ,
(
SELECT b.number_of_seat - sum(booking.number_of_seat)-sum(reserved_seats.number_of_reserved_seat)
FROM bus_routines AS r
INNER JOIN buses AS b
ON b.id = r.bus_id
INNER JOIN
(SELECT number_of_seat , bus_routine_id FROM booking GROUP BY booking.bus_routine_id) AS booking
ON booking.bus_routine_id = r.id
INNER JOIN (SELECT number_of_reserved_seat , routine_id FROM reserved_seats GROUP BY reserved_seats.routine_id) AS reserved_seats
ON r.id = reserved_seats.routine_id
WHERE
r.sector_from = "KTM" AND
r.sector_to = "PKR" AND
r.departure_date = "2015-12-15"
) AS avaliable_seat
FROM bus_routines AS r
INNER JOIN buses AS b
ON b.id = r.bus_id
WHERE
r.sector_from = "KTM" AND
r.sector_to = "PKR" AND
r.departure_date = "2015-12-15"
HAVING avaliable_seat > 0
对于所有行
我也尝试了另一个查询，但它给了我单一的结果
avaliable_seat我还尝试了另一个查询，它给了我Subquery返回超过1行。查询是
SELECT r.* , b.* , b.number_of_seat - sum(booking.number_of_seat)-sum(reserved_seats.number_of_reserved_seat) AS available_seat
FROM bus_routines AS r
INNER JOIN buses AS b
ON b.id = r.bus_id
INNER JOIN
(SELECT number_of_seat , bus_routine_id FROM booking GROUP BY booking.bus_routine_id) AS booking
ON booking.bus_routine_id = r.id
INNER JOIN
(SELECT number_of_reserved_seat , routine_id FROM reserved_seats GROUP BY reserved_seats.routine_id) AS reserved_seats
ON r.id = reserved_seats.routine_id
WHERE
r.sector_from = "KTM" AND
r.sector_to = "PKR" AND
r.departure_date = "2015-12-15"
HAVING available_seat > 0
答案 0 :(得分：0)
一种方法是使用相关子查询来获取每个reserved_seats的{{1}}和booked_seats。
我们假设此查询返回您要返回的行，它只是缺少您想要计算的bus_routine列：
available_seat预约席位的数量＆＃34;对于给定的bus_routine，您可以查询SELECT r.*
, b.*
FROM bus_routines r
JOIN buses b
ON b.id = r.bus_id
WHERE r.sector_from = 'KTM'
AND r.sector_to = 'PKR'
AND r.departure_date = '2015-12-15'
表，如下所示：
reserved_seats＆＃34;预订座位的数量＆＃34;对于给定的SELECT IFNULL(SUM(s.number_of_reserved_seat),0)
FROM reserved_seats s
WHERE s.routine_id = '649'
，可以从bus_routine表返回，如下所示：
booking我们可以将查询纳入＆＃34;保留席位＆＃34;和＃34;预订座位＆＃34;进入第一个查询，作为相关子查询。代替文字SELECT IFNULL(SUM(k.number_of_seat),0)
FROM booking k
WHERE k.bus_routine_id = '649'
，引用'649'表中的id。
bus_routine如果没有要求返回SELECT r.*
, b.*
-- number of booked seats
, ( SELECT IFNULL(SUM(k.number_of_seat),0)
FROM booking k
WHERE k.bus_routine_id = r.id
) AS booked_seats
-- number of reserved seats
, ( SELECT IFNULL(SUM(s.number_of_reserved_seat),0)
FROM reserved_seats s
WHERE s.routine_id = r.id
) AS reserved_seats
-- calculate available seats as
-- (bus number_of_seat) - (booked_seats) - (reserved_seats)
, ( b.number_of_seat
- ( SELECT IFNULL(SUM(k.number_of_seat),0)
FROM booking k
WHERE k.bus_routine_id = r.id
)
- ( SELECT IFNULL(SUM(s.number_of_reserved_seat),0)
FROM reserved_seats s
WHERE s.routine_id = r.id
)
) AS avaliable_seat
FROM bus_routines r
JOIN buses b
ON b.id = r.bus_id
WHERE r.sector_from = 'KTM'
AND r.sector_to = 'PKR'
AND r.departure_date = '2015-12-15'
和booked_seats列，则可以从查询中省略这些列。获取这些值的子查询只能出现在reserved_seats列的计算中。
SQL Fiddle demonstration here: http://sqlfiddle.com/#!9/64eaa/7
答案 1 :(得分：-1)