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我正在尝试编写一个查询来显示每位乘客的姓名及其票价。这是我到目前为止所拥有的——它没有给出错误，但也没有结果：

-- Write a query to display the Name of each passenger as well as the fare for their trip.
select passenger.name, departure_info.fare * passenger.quantity AS passenger_fare
from passenger, seat_passenger, manages, departure_info, seat_info
where departure_info.Dept_id=manages.Dept_id 
AND manages.Seat_id=seat_info.Seat_id 
AND seat_info.Seat_id=seat_passenger.Seat_id 
AND seat_passenger.Pass_id=passenger.pass_id

这是表http://i.imgur.com/R4EFthY.png的关系视图

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1 回答 1

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使用正确的连接语法将从您的查询中生成此查询

select
    p.name, di.fare * p.quantity as passenger_fare
from passenger as p
   inner join seat_passenger as sp on sp.pass_id = p.pass_id
   inner join seat_info as si on si.seat_id = sp.seat_id
   inner join manages as m on m.seat_id = si.seat_id
   inner join departure_info as di on di.dept_it = m.dept_id

我建议你转身看看你错过了inner joins什么left outer joins

select
    p.name, di.fare * p.quantity as passenger_fare,
    sp.pass_id, si.seat_id, m.seat_id, di.dept_id
from passenger as p
   left outer join seat_passenger as sp on sp.pass_id = p.pass_id
   left outer join seat_info as si on si.seat_id = sp.seat_id
   left outer join manages as m on m.seat_id = si.seat_id
   left outer join departure_info as di on di.dept_it = m.dept_id

实际上，您甚至可以删除未使用的连接（如果您没有错过来自 seat_info 的一些记录）：

select
    p.name, di.fare * p.quantity as passenger_fare
from passenger as p
   inner join seat_passenger as sp on sp.pass_id = p.pass_id
   inner join manages as m on m.seat_id = sp.seat_id
   inner join departure_info as di on di.dept_it = m.dept_id
于 2013-08-06T02:55:24.013 回答