django 笔记5 外键 ForeignKey

class UsserGroup(models.Model):
    uid = models.AutoField(primary_key=True)
    caption = models.CharField(max_lenght=, unique=True)

class UserInfo(models.Model):
    username = models.CharField(max_length=,blank=True,verbose_name = '用户名')
    password = models.CharField(max_length=, help_text='pwd')
    #外键  to_field不写也行，以默认主键  会将user_group生成为user_group_id 数字
    user_group = models.ForeignKey('UserGroup', to_field = 'uid',default=,on_delete=models.CASCADE)

    特殊地方 user_group 封装为一个对象 可以直接调用UserGroup的参数 即user_group.caption    而user_group_id为数字
user_list = Userinfo.objects.all()
for row in user_list:
    print(row.user_group_id)
    print(row.user_group.uid)
    print(row.user_group.caption)

    #一对多
    #user_list = models.UserInfo.object.all(
    username = 'root'
    password='',
    user_group_id = ''  #直接用表里面user_group中 让他设置为user_group_id
    )

    让用户选择部门
    group_list = models.UserGroup.object.all()

    在html里写
    <form>
    <select name = 'group_id'>
        {% for item in group_list %}
            <option value='{{item.uid}}'>{{ item.caption }}</option>
        {% endfor %}
    </select>
    <form>

一对多:
    a.外键
    b.外键字段_id
    c. models.tb.object.create(name='root'),user_group_id =
    d.
        userlist = models.tb.object.all()
        for row in userlist:
            row.id
            row.user_group_id
            row.user_group.caption