# 关联外键    

sgrade = models.ForeignKey("Grades",on_delete=models.CASCADE)

版本跟新后忘记加on_delete=models.CASCADE

报错困扰了很久 多读报错信息

from django.db import models# Create your models here.
class Grades(models.Model):gname = models.CharField(max_length=20)gdate = models.DateTimeField()ggirlnum = models.IntegerField()gboynum = models.IntegerField()isDelete = models.BooleanField(default=False)def __str__(self):return self.gnameclass Meta:db_table = "grades"
#
class StudentsManager(models.Manager):def get_queryset(self):return super(StudentsManager,self).get_queryset().filter(isDelete=False)class Students(models.Model):#自定义模型管理器#当自定义模型管理器，object就不存在了stuObj =models.Manager()stuObj2=StudentsManager()sname = models.CharField(max_length=20)sgender = models.BooleanField(default=True)sage = models.IntegerField(db_column='age')scontend = models.CharField(max_length=20)isDelete = models.BooleanField(default=False)#关联外键sgrade = models.ForeignKey("Grades",on_delete=models.CASCADE)def __str__(self):return self.sname# lastTime = models.DateTimeField(auto_created=True)# createTime = models.DateTimeField(auto_created=True)class Meta:db_table = "students"ordering = ['id']