Django ORM 更好的方法来操作 Django ORM 查询

Question

型号如下：

class Seat(models.Model):
    hall = models.ForeignKey(Hall,on_delete=CASCADE)
    type = models.TextField(verbose_name="Seat Type")

class Show(models.Model):
    show_time = models.TimeField(verbose_name='Show Time')
    movie = models.ForeignKey(Movie,on_delete=CASCADE)
    hall = models.ForeignKey(Hall,on_delete=CASCADE)
    cinema = models.ForeignKey(Cinema,on_delete=CASCADE)

class Booking(models.Model):
    seat = models.ForeignKey(Seat,on_delete=CASCADE)
    show = models.ForeignKey(Show,on_delete=CASCADE)
    movie = models.ForeignKey(Movie,on_delete=CASCADE)
    hall = models.ForeignKey(Hall,on_delete=CASCADE)
    cinema = models.ForeignKey(Cinema,on_delete=CASCADE)
    user = models.ForeignKey(User, verbose_name="Username", on_delete=DO_NOTHING) # donothing

型号说明：

Multiple Seats in a Hall

Each Hall hosts multiple Shows

Each Booking is basically a ticket for a show with a specific seat and a specific show.

要求是获取一个查询集，其中包含特定演出的预订 table 中不存在的所有座位。基本上，通过检查 Bookings table

中是否存在可用座位列表来获取节目的可用座位列表

SQL 查询如下所示：

SELECT * FROM Seat as S join Show as Sh on S.hall = Sh.hall join Bookings as B on B.show = Sh.id where Sh.id = 1 AND B.seat IS NULL

如何将其转换为 Django ORM：

可以这样做（有没有比创建 seat_id_list 更好的方法？）：

            qs = Seat.objects.filter(hall=hid) #----------------------------------
            show_bookings = Booking.objects.filter(show=spk)
            seat_id_list = []

            for each_booking in show_bookings:
                print(each_booking.seat.id)
                seat_id_list.append(each_booking.seat.id)
            qss = Seat.objects.exclude(id__in = seat_id_list)

Answer 1

您可以通过以下方式获得这些 Seat：

Seat.objects.filter(<strong>hall=hid</strong>).exclude(<strong>booking__show=spk</strong>)

这将检索给定 Hall 对象 hid 的所有 Seat，其中 Show 没有 Booking 由 spk对象。

Django ORM 更好的方法来操作 Django ORM 查询

Django ORM better way to manipulate django ORM query

python

django

django-models

django-orm

django-views