Django 之 Models（Models 模型 & 数据表关系）

           # django 连接 mysql

           DATABASES = [

               'default' = {

                   'ENGINE': 'django.db.backends.mysql',

                   'NAME': '数据库名',

                   'PASSWORD': '数据库密码',

                   'HOST': '127.0.0.1',

                   'PORT': '3306', 

               }

           ]

   - 需要在项目文件下的__init__文件中导入pymysql包        
   

       ```python

       # 在主项目的__init__文件中

       import pymysql   

       pymysql.install_as_MySQLdb()

       ```

       python3 manage.py makemigrations

       python3 manage.py migrate

       # 如果迁移过程中出现没有变化或者报错，可以尝试强制迁移

       # 强制迁移命令

       python3 manage.py makemigrations 应用名

       python3 manage.py migrate 应用名

1. 启动命令行: python3 manage.py shell
ps: 注意点: 对orm的操作分为静态函数和非静态函数两种，静态是指在内存中只有一份内容存在，调用的时候使用 类名. 的方式，如果修改了那么所有使用的人都会受影响
2. 在命令行中导入对应的映射类
    from 应用.models import 类名
3. 使用 objects 属性操作数据库，objects 是模型中实际和数据库进行交互的 Manager 类的实例化对象
4. 查询命令
    - 类名.objects.all() 查询数据表中的所有内容，返回的结果是一个 QuerySet 类型，实际上是类列表中装这个一个一个数据对象
    - 类名.objects.filter(条件)

# from 应用名.models import 类名
from myapp.models import Student

# 查询Student表中的所有数据,得到的是一个QuerySet类型
Student.objects.all()

# 如果要取出所有QuerySet类型中的所有数据对象,需要遍历取出所有的对象,再用对象.属性来查看值
s = Student.object.all()
for each in s:
	print(each.name , each.age , each.address , each.phone)

# 如果要进行过滤筛选,使用filter()方法
Student.objects.filter(age=18)

对象 = 类()   # 使用类实例化对象
对象.属性 = 值  # 给对应的对象的属性赋值
对象.save()  # 必须要执行保存操作,否则数据没有进入数据库


# python3 manage.py shell 命令行中添加数据

# from 应用名.models import 类名

from myapp.models import Student

# 实例化对象
s = Student()

# 给对象的属性赋值
s.name = 'ruochen'
s.address = 'xxx'
s.phone = '18888888888'
s.age = 18

# 保存数据
s.save()

# 查找年龄大于18的老师
ta = Teacher.objects.filter(age__gt=18)

# 小于20
ta = Teacher.objects.filter(age__lt=20)

# 查找course中包含a字母的老师
ta = Teacher.objects.filter(course__contains="a")

       s = School()

       s.school_id = 2

       s.school_name = "sssss"

       s.save() 

       # 方法一

       m = Manager()

       m.manager_id = 10

       m.manager_name = "ruochen"

       m.my_school = s

       m.save()

       # 方法二

       m = Manager.objects.create(manager_id=20, manager_name="ruo", my_school=ss[0])

       Manager.objects.get(manager_name="ruochen").my_school.school_name

      In [43]: s = School.objects.get(manager__manager_name="ruochen")

      In [44]: s

      Out[44]: <School: sssss>

       In [47]: s.school_name = "111"

       In [48]: s.save()

       In [53]: ss = School.objects.all()

       In [54]: type(ss)

       Out[54]: django.db.models.query.QuerySet

       In [55]: ss.update(school_name="666")

       Out[55]: 2

       In [57]: ss

       Out[57]: [<School: 666>, <School: 666>

       # 方法一

       In [3]: t1 = Teacher()

       In [4]: t1.teacher_name = "若尘"

       In [5]: t1.my_school = ss[0]

       In [6]: t1.save()

       In [7]: ts = Teacher.objects.all()

       In [8]: ts

       Out[8]: [<Teacher: Teacher object>]

       In [9]: ts[0].teacher_name

       Out[9]: '若尘'

       # 方法二

       In [21]: t2 = Teacher.objects.create(teacher_name="ruochen2", my_school=ss[0])

       In [22]: ts = Teacher.objects.all()

       In [23]: ts

       Out[23]: [<Teacher: Teacher object>, <Teacher: Teacher object>]

       In [24]: ts[1].teacher_name

       Out[24]: 'ruochen2'

       In [30]: t1.my_school

       Out[30]: <School: 666>

           In [34]: s1.teacher_set.all()

           Out[34]: [<Teacher: Teacher object>, <Teacher: Teacher object>]

           In [36]: s1.teacher_set.all().filter(teacher_name="若尘")

           Out[36]: [<Teacher: Teacher object>]

       In [2]: stus = Student.objects.all()

       In [3]: stus

       Out[3]: []

       In [4]: s1 = Student()

       In [5]: s1.student_name = "ruochen"

       In [6]:

       In [6]: t1 = Teacher.objects.all()

       In [7]: t1

       Out[7]: [<Teacher: Teacher object>, <Teacher: Teacher object>]

       In [9]: t1.teacher_name

       Out[9]: '若尘'

       In [12]: s1.save()

       In [17]: s1.teachers.add(t1)

       In [18]: s1.teachers.all()

       Out[18]: [<Teacher: Teacher object>]

       In [19]: s1.save()

       In [24]: s1.teachers.all()[0].teacher_name

       Out[24]: '若尘'

       In [25]: t1.student_set.all()

       Out[25]: [<Student: Student object>]