Room
    id

    1

    2

    ..

        1000

User:

    id

    1

    ..

    10000

Booking:

    user_id   room_id    time_id       date

       1          1                8:00      2017-11-11

       1          2                8:00      2017-11-11

       1          3                8:00      2017-11-11

       1          4                8:00      2017-11-11

       1          5                8:00      2017-11-11

# 解决方案一：执行11次sql语句

bk = models.Booking.objects.filter(date=2018-11-11)

for item in bk:

    print(item.time_id, item.room.caption, item.user.user)

# 解决方案二：执行1次

#select * from ... left join user ... join room

bk = models.Booking.objects.filter(date=2018-11-11).select_related('user','room')

for item in bk:

    print(item.time_id, item.room.caption, item.user.user)

# 解决方案三：执行3次

#select * from booking where date=2018-11-11

#select * from user where id in [1,]

#select * from room where id in [1,2,3,4,5]

bk = models.Booking.objects.filter(date=2018-11-11).prefetch_related('user','room')

for item in bk:

    print(item.time_id, item.room.caption, item.user.user)

    1.     [{} ]

        all_users = models.User.objects.all().values('name','age','role__name')

    2. [ 对象 ]

        all_users = models.User.objects.all()

        用的时候注意，只拿自己表中的字段，别跨表

    3. select_related  （外键、一对一）

        all_users = models.User.objects.all().select_related('role')

    4. prefetch_related （role）

        all_users = models.User.objects.all().prefetch_related('role')

    5. only

        all_users = models.User.objects.all().only('name')

        用的时候注意，只拿自己指定的字段

    6. defer

        all_users = models.User.objects.all().defer('name')

 　　　　　　 remove_booking = Q()

            for room_id, time_id_list in booking_info['del'].items():

                for time_id in time_id_list:

                    temp = Q()    #实例化一个Q对象

                    temp.connector = 'AND'  #以and的方式连接

                    # user_id是一个字段，后面的是一个字段对应的值

                    temp.children.append(('user_id', request.session['user_info']['id'],))

                    temp.children.append(('booking_date', booking_date,))

                    temp.children.append(('room_id', room_id,))

                    temp.children.append(('booking_time', time_id,))

                    remove_booking.add(temp, 'OR')   #以or的方式添加到temp