python - django - 如何将表的记录与来自另一个表的计算计数值绑定(bind)

Question

在我的应用程序中，我有一个培训列表。此列表中的一个字段应显示每个培训的预订数量。为了说明我的意思，我准备了 SQL 查询:

SELECT *
FROM club_training a
LEFT JOIN
(SELECT training_id, count(*)
FROM club_booking
group by training_id) b
ON a.id = b.training_id

你能给我一些建议如何在 Django 中做到这一点吗？我在我的代码中使用了 Booking.objects.all().values('training_id').annotate(booked_amount=Count('training_id'))，但结果是所有训练的所有计数值为列表中的每个训练显示。应显示一个适合每次训练的计数值。

View .py

class HomePageView(TemplateView):
    """Home Page with list of trainings"""
    template_name = 'club/training_list.html'


    def get_context_data(self, **kwargs):
        now = datetime.datetime.now()
        context = super(HomePageView, self).get_context_data(**kwargs)
        context['trainings'] = Training.objects.filter(state="A", training_date__gte=now).order_by('training_date', 'start_time')
        for each_training in context['trainings']:       
            each_training.diff = each_training.availability - each_training.counter
            each_training.counter = Booking.objects.all().values('training_id').annotate(booked_amount=Count('training_id'))
        return context 

模型.py

class Training(models.Model):
    """Class for plan training"""
    STATE = (
        ('A', 'Active'),
        ('I', 'Inactive'),
    )
    name = models.ForeignKey('TrnDesc')
    instructor = models.ForeignKey('Instructor')
    start_time = models.TimeField(blank=True)
    end_time = models.TimeField(default='00:00:00')
    availability = models.PositiveIntegerField(default=15)
    state = models.CharField(max_length=1, choices=STATE, default='A')
    training_date = models.DateField(default=date.today)
    counter = models.PositiveIntegerField(default=0)
    def __str__(self):
        return self.name.name

class Booking(models.Model):
    """Data of people which book fitness classes"""
    first_name = models.CharField(max_length=50)
    last_name = models.CharField(max_length=50)
    email = models.CharField(max_length=50)
    phone = models.CharField(max_length=10)
    training = models.ForeignKey('Training')
    def __str__(self):
        return self.training.name.name

training_list.html

{% extends 'club/base.html' %}

{% block content %}

        <ul class="nav nav-pills">
            <li role="presentation" class="active"><a href="#">Fitness Classes</a></li>
            <li role="presentation"><a href="#">Join Us</a></li>
            <li role="presentation"><a href="#">Contact Us</a></li>
        </ul>
        <br></br>
    {% regroup trainings by training_date as date_list %}
    {% for date in date_list %}
        <div class="panel panel-default">


            <div class="panel-heading">{{date.grouper|date:"l, d F o"}}</div>


            <table class="table">
                <tr>
                    <th style="width: 20%">Training name</th>
                    <th style="width: 30%">Training description</th>
                    <th style="width: 10%">Instructor</th>
                    <th style="width: 10%">Start time</th>
                    <th style="width: 10%">End time</th>
                    <th style="width: 10%">Left</th>
                    <th style="width: 10%">Test_counter</th>
                    <th style="width: 10%">Actions</th>
                </tr>


                {% for training in date.list %}

                <tr>
                    <td>{{training.name}}</td>
                    <td>{{training.name.desc}}</td>
                    <td>{{training.instructor}}</td>
                    <td>{{training.start_time|time:"H:i"}}</td>
                    <td>{{training.end_time|time:"H:i"}}</td>
                    <td>{{training.diff}}</td>
                    <td>{{training.counter}}</td>
                    <td><a href="{% url 'book' training_id=training.pk%}"><button type="button" class="btn btn-primary">Book</button></a></td>
                </tr>

                {% endfor %}    
            </table>
        </div>
    {% endfor %}

{% endblock %}

Answer 1

 for each_training in context['trainings']:       
        each_training.diff = each_training.availability - each_training.counter
        each_training.counter = Booking.objects.filter(training_id=each_training.id).count()  # just modify this line
    return context