知识要点：

表关系的实现

一对多表关系

在Mysql中一对多是通过外键实现的，在django模型中通过ForeignKeyfield类型实现。

一对一表关系

在Mysql中一对一是通过外键加唯一键实现的，在django模型中通过OneToOneField类型实现。

多对多表关系

在Mysql中多对多是通过中间表外键加联合唯一键实现的，在django模型中通过ManyToManyField类型实现。中间表模型会自动帮我们创建好。

例子：

class Department(models.Model):
    d_id = models.AutoField(primary_key=True)
    d_name = models.CharField(max_length=30)
    def __str__(self):
        return 'Department<d_id=%s,d_name=%s>'%(
            self.d_id,self.d_name
        )

class Student(models.Model):
    s_id = models.AutoField(primary_key=True)
    s_name = models.CharField(max_length=30)
    department = models.ForeignKey('Department')
    course = models.ManyToManyField('Course')
    def __str__(self):
        return 'Student<s_id=%s,s_name=%s>'%(
            self.s_id,self.s_name
        )


class Course(models.Model):
    c_id = models.AutoField(primary_key=True)
    c_name = models.CharField(max_length=30)
    def __str__(self):
        return 'Course<c_id=%s,c_name=%s>'%(
            self.c_id,self.c_name
        )

class Stu_detail(models.Model):
    s_id = models.OneToOneField('Student')
    age = models.IntegerField()
    gender = models.BooleanField(default=1)
    country = models.CharField(max_length=30,null=True)
    def __str__(self):
        return 'Stu_detail<s_id=%s,age=%s,gender=%s,country=%s>'%(
            self.s_id,self.age,self.gender,self.country
        )

关系表中数据的操作

from .models import Department,Student,Course
def add_info(request):
    # d1 = Department(d_name='CC')
    # d1.save()
    # 一对多关系加内容
    # s1 = Student(s_name='xiaoming')
    # s1.department = d1
    # s1.save()
    # 多对多关系添加内容
    # c1 = Course(c_name='python')
    # s1 = Student.objects.first()
    # c1.save()
    # s1.course.add(c1)
    return HttpResponse('添加数据成功')
    
def search_info(request):
    rs = Student.objects.all()[0]
    # 一对多的查询
    print(rs.department)
    # 多对多的正向查询
    print(rs.course.all())
    cs = Course.objects.first()
    # 多对多反向查询
    print(cs.student_set.all())
    return HttpResponse('查询数据成功')