小白学习django第四站-关联数据库

时间：2021-09-02 13:31:36

使用mysql连接django首先要配置好相关环境

首先在setting.py配置数据库信息（需要现在mysql中创建一个数据库）

小白学习django第四站-关联数据库

在setting.py那个目录的__init__.py文件中写入

小白学习django第四站-关联数据库

之后就可以在app目录的models.py文件中编写django的模型类

from django.db import models

# Create your models here.

# 1、创建模型类

# 表映射关系 模型类 == 表 属性 == 字段

class User(models.Model):

    id = models.AutoField(primary_key=True)     # 自增长主键列，默认的

    name = models.CharField(max_length=30)

    city = models.CharField(max_length=30, default='beijing')

    age = models.IntegerField(default=18)

    # 2、创建一个映射文件（迁移）

    # python manage.py makemigrations [appanme]

    # 3、 将映射文件的映射数据真正提交到数据库（迁移）

    #  python manage.py migrate [appname]

    def __str__(self):

        return 'id=%s, name=%s, city=%s, age=%s' % (self.id, self.name, self.city, self.age)

然后点击

小白学习django第四站-关联数据库

在下面命令行输入

makemigrations [appname] 这个是用来创建映射文件的

在输入

migrate [appname] 这个是将映射数据提交到数据库中

这样数据库中表就建立好了

之后就可以编写增删改查操作了

from django.shortcuts import render

from django.http import HttpResponse

# Create your views here.

from .models import User

def add(request):

    # # 方法一

    # mr = User(name='xuning', city='beijing')

    # mr.save()   # 保存提交

    # 方法二

    # mr = User()

    # mr.name = 'test1'

    # mr.city = 'chengdu'

    # mr.save()

    # 方法三

    # User.objects.create(name='test2', city='辽宁')

    # User.objects.create(name='test3', city='铁岭')

    # 方法四

    # User.objects.get_or_create(name='test4', city='北京')    # 判断你有没有重复的数据

    return HttpResponse('添加成功')

def select(request):

    # 查询所有对象

    # rs = User.objects.all()

    # print(rs[0])

    # 查询单个对象

    # rs = User.objects.get(city='长春')

    # 查询满足条件的对象

    # rs = User.objects.filter(name='xuning' or 'test1')

    # return HttpResponse('查询成功')

    # 查询第一条数据

    # rs = User.objects.first()

    # 查询最后一条数据

    # rs = User.objects.last()

    # 查询不满足条件的

    # rs = User.objects.exclude(name='test2')

    # 对于查询结果进行排序

    # rs = User.objects.order_by('age')

    # 对于查询结果进行排序，反序

    # rs = User.objects.order_by('-age')

    # 对于查询结果进行排序，多个

    # rs = User.objects.order_by('age', 'id')

    # 对查询结果转换成字典

    # rs = User.objects.all().values()

    # 对于查询总数进行计数

    # rs = User.objects.all().count()

    # 查询条件

    # 相当于等于

    # rs = User.objects.filter(name__exact='test3')   # 不区分大小写

    # 包含,模糊查询

    # rs = User.objects.filter(name__contains='test')

    # 以什么开头

    # rs = User.objects.filter(name__istartswith='t')

    # 以什么结尾

    # rs = User.objects.filter(name__iendswith='4')

    # 成员所属

    # rs = User.objects.filter(age__in=[3, 18, 20])

    # rs = User.objects.filter(id__in=[3, 4, 5])

    # 大于 大于等于 小于 小于等于

    # rs = User.objects.filter(age__lte=18)

    # 区间

    # rs = User.objects.filter(age__range=(2, 18))

    # 切片

    rs = User.objects.all()[0:3]

    # rs = User.objects.filter(name__contains='tes') & User.objects.filter(id=2)

    return render(request, 'db_index.html', context={'rs': rs})

def update(request):

    # rs = Dog.objects.get(id=2)

    # print(rs)

    # rs.name = 'test'

    # rs.age = 20

    # rs.save()

    # User.objects.filter(name='test1').update(city='长春')

    # User.objects.all().update(city='长春')

    # User.objects.filter(id=5).update(name='test5')

    # User.objects.filter(id=6).update(name='test6')

    # Dog.objects.filter(name='test1').update(age=30)

    # Course.objects.filter(c_id=1).update(c_name='python')

    return HttpResponse('修改成功')

def delete(request):

    # User.objects.get(name='test').delete()

    # Student.objects.all().delete()

    # Stu_detail.objects.all().delete()

    # Department.objects.all().delete()

    # Course.objects.all().delete()

    return HttpResponse('删除成功')

变关系的实现（一对多， 一对一， 多对多）

先建立表模型



from django.db import models


class Department(models.Model):

    d_id = models.AutoField(primary_key=True)

    d_name = models.CharField(max_length=30)

    def __str__(self):

        return f'Department<d_id={self.d_id}, d_name={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', on_delete=models.CASCADE, null=True)  # 级联删除

    # department = models.ForeignKey('Department', on_delete=models.SET_NULL, null=True)  # 级联删除

    # department = models.ForeignKey('Department', on_delete=models.PROTECT, null=True)  # 级联删除

    # course = models.ManyToManyField('Course')

    def __str__(self):

        return f'Student<s_id={self.s_id}, s_name={self.s_name}>'

class Course(models.Model):

    c_id = models.AutoField(primary_key=True)

    c_name = models.CharField(max_length=30)

    student = models.ManyToManyField('Student')

    def __str__(self):

        return f'Course<c_id={self.c_id}, c_name={self.c_name}>'

class Stu_detail(models.Model):

    # s_id = models.OneToOneField('Student', on_delete=models.CASCADE)

    student = models.OneToOneField('Student', on_delete=models.CASCADE)

    age = models.IntegerField()

    gender = models.BooleanField(default=1)

    city = models.CharField(max_length=30, null=True)

    def __str__(self):

        return f'Stu_detail<s_id={self.student}, age={self.age}, gender={self.gender}, city={self.city}>'

# 级联删除 保证数据的完整性与一致性

# on_delete=models.CASCADE  删除主键同时删除外键数据

# on_delete=models.SET_NULL null=True 删除主键同时把外键设置为空

# on_delete=models.PROTECT  如果有外键正在引入主键， 那么主键不允许删除




之后对表关系进行操作




from django.shortcuts import render

from django.http import HttpResponse

# Create your views here.

from .models import User, Department, Student, Course, Stu_detail

def func2(request):

    # # 为学院表添加数据

    # Department.objects.get_or_create(d_name='软件')

    # Department.objects.get_or_create(d_name='化学')

    # Department.objects.get_or_create(d_name='物理')

    # Department.objects.get_or_create(d_name='数学')

    # Department.objects.get_or_create(d_name='语言')

    # Department.objects.get_or_create(d_name='历史')

    # # 为学生添加数据

    # Student.objects.get_or_create(s_name='test1', department_id=1)

    # Student.objects.get_or_create(s_name='test2', department_id=1)

    # Student.objects.get_or_create(s_name='test3', department_id=1)

    # Student.objects.get_or_create(s_name='test4', department_id=2)

    # Student.objects.get_or_create(s_name='test5', department_id=2)

    # Student.objects.get_or_create(s_name='test6', department_id=3)

    # Student.objects.get_or_create(s_name='test7', department_id=4)

    # Student.objects.get_or_create(s_name='test8', department_id=5)

    # Student.objects.get_or_create(s_name='test9', department_id=6)

    # # 为学生信息添加数据

    # Stu_detail.objects.get_or_create(age=18, gender=1, city='上海', student_id=1)

    # Stu_detail.objects.get_or_create(age=17, gender=0, city='武汉', student_id=2)

    # Stu_detail.objects.get_or_create(age=18, gender=1, city='长沙', student_id=3)

    # Stu_detail.objects.get_or_create(age=19, gender=1, city='北京', student_id=4)

    # Stu_detail.objects.get_or_create(age=16, gender=1, city='长春', student_id=5)

    # Stu_detail.objects.get_or_create(age=17, gender=0, city='铁岭', student_id=6)

    # Stu_detail.objects.get_or_create(age=18, gender=1, city='南京', student_id=7)

    # Stu_detail.objects.get_or_create(age=16, gender=0, city='天津', student_id=8)

    # Stu_detail.objects.get_or_create(age=17, gender=1, city='西安', student_id=9)

    # # 为课程添加信息

    # Course.objects.get_or_create(c_name='pyhton')

    # Course.objects.get_or_create(c_name='c++')

    # Course.objects.get_or_create(c_name='php')

    # Course.objects.get_or_create(c_name='java')

    # Course.objects.get_or_create(c_name='go')

    # Course.objects.get_or_create(c_name='r')

    # 一对多操作

    d1 = Department.objects.get(d_id=1)

    d2 = Department.objects.get(d_id=2)

    d3 = Department.objects.get(d_id=3)

    s1 = Student.objects.get(s_id=1)

    s2 = Student.objects.get(s_id=2)

    s3 = Student.objects.get(s_id=3)

    s7 = Student.objects.get(s_id=7)

    # add方法

    # 将学生s_id2添加到学院d_id2中

    # d2.student_set.add(s2)

    # d1.student_set.add(s7)

    # create方法

    # 新建学生test10，加入d_id1中

    # d1.student_set.create(s_name='test10')

    # 查询

    # print(s1.department.d_name)

    # print(s1.department.d_id)

    # print(d1.student_set.all())

    # print(d1.student_set.filter(s_id=1))

    # print(d1.student_set.get(s_id=3))

    # 删除

    # d1.student_set.remove(s3)

    # d2.student_set.clear()

    # 一对一操作

    # stu = Stu_detail.objects.get(id=1)

    # print(stu.student.s_name)

    # print(s1.stu_detail.city)

    # 多对多操作

    c1 = Course.objects.get(c_id=1)

    c2 = Course.objects.get(c_id=2)

    c3 = Course.objects.get(c_id=3)

    c4 = Course.objects.get(c_id=4)

    s6 = Student.objects.get(s_id=6)

    s7 = Student.objects.get(s_id=7)

    s8 = Student.objects.get(s_id=8)

    s9 = Student.objects.get(s_id=9)

    # 添加

    # c1.student.add(s6, s7)

    # s8.course_set.add(c2, c4)

    # s9.course_set.add(c1, c3)

    # 查询

    # print(s6.course_set.all())

    # print(s7.course_set.get(c_id=1))

    # print(c2.student.all())

    # print(c3.student.get(s_id=9))

    # 删除

    # s6.course_set.remove(c1)

    # c4.student.clear()

    # c3.student.remove(s9)

    # 多表联查

    # 查询报名了python的学生的学生信息

    # rs = Stu_detail.objects.filter(student__course__c_name='python')

    # rs = Stu_detail.objects.filter(student__course__c_id=1)

    # 学生名字包含test1的学院信息

    # rs = Department.objects.filter(student__s_name__contains='test')

    # 软件学院报名了python的学员的详细信息

    # rs = Stu_detail.objects.filter(student__department__d_name='软件', student__course__c_name='python')

    # print(rs)

    return HttpResponse('执行成功')


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