多表查询实例

from django.db import models

# Create your models here.

# 1.老师表
class Teacher(models.Model):

    tid =  models.AutoField(primary_key=True)
    tname = models.CharField(max_length=32)

    class Meta:
        db_table="teacher"
    def __str__(self):
        return self.tname

# 2.课程表
class Course(models.Model):
    cid =  models.AutoField(primary_key=True)
    cname = models.CharField(max_length=32)
    #老师和课程 一对多
    teaher =models.ForeignKey(to="Teacher",on_delete=models.CASCADE)
    class Meta:
        db_table="course"

#3. 年纪表
class Class_grade(models.Model):
    gid = models.AutoField(primary_key=True)
    gname = models.CharField(max_length=32)
    class Meta:
        db_table="grade"


#4.班级表
class Class(models.Model):
    cid = models.AutoField(primary_key=True)
    caption = models.CharField(max_length=32)
    #年级和班级是一对多关系
    calss_grade = models.ForeignKey(to="Class_grade", on_delete=models.CASCADE)
    #班级和老师多对多
    teahcer=models.ManyToManyField(to="Teacher")
    class Meta:
        db_table="class"

#5.学生表
class Student(models.Model):
    sid = models.AutoField(primary_key=True)
    sname = models.CharField(max_length=32)
    gender = models.CharField(max_length=32)
    #学生表和班级表 多对一
    cls= models.ForeignKey(to="Class",on_delete=models.CASCADE)
    class Meta:
        db_table="student"



#6.成绩表
class Score(models.Model):
    sid = models.AutoField(primary_key=True)
    score =models.IntegerField()

    # #成绩和课程一对多
    #
    course =models.ForeignKey(to="Course", on_delete=models.CASCADE)
    # #成绩和学生一对多
    student = models.ForeignKey(to="Student", on_delete=models.CASCADE)
    class Meta:
        db_table="score"
    #