Django模型类之models字段类型和参数以及元数据meta

# class Test(models.Model): ?# courses_test# ????"""测试学习用"""# ????# Auto = models.AutoField() ?# 自增长字段# ????# BigAuto = models.BigAutoField()## ????# 二进制数据# ????Binary = models.BinaryField()## ????# 布尔型# ????Boolean = models.BooleanField()# ????NullBoolean = models.NullBooleanField()## ????# 整型# ????PositiveSmallInteger = models.PositiveSmallIntegerField(db_column="age") ?# 5个字节# ????SmallInteger = models.SmallIntegerField(primary_key=False) ?# 6个字节# ????PositiveInteger = models.PositiveIntegerField() ?# 10个字节# ????Integer = models.IntegerField(verbose_name="11个字节大小") ?# 11个字节# ????BigInteger = models.BigIntegerField(unique=True) ?# 20个字节## ????# 字符串类型# ????Char = models.CharField(max_length=100, null=True, blank=True, db_index=True) ?# varchar# ????Text = models.TextField(help_text="这个是longtext") ?# longtext## ????# 时间日期类型# ????Date = models.DateField(unique_for_date=True, auto_now=True) ?#自动填入最新时间# ????DateTime = models.DateTimeField(editable=False, unique_for_month=True, auto_now_add=True)# ????Duration = models.DurationField() ?# int, Python timedelta实现## ????# 浮点型# ????Float = models.FloatField()# ????Decimal = models.DecimalField(max_digits=4, decimal_places=2) ?# 11.22, 16.34## ????# 其它字段# ????Email = models.EmailField() ?# 邮箱# ????Image = models.ImageField()# ????File = models.FileField()# ????FilePath = models.FilePathField()# ????URL = models.URLField()# ????UUID = models.UUIDField()# ????GenericIPAddress = models.GenericIPAddressField()### class A(models.Model):# ????onetoone = models.OneToOneField(Test, related_name="one")### on_delete 六种模式# class B(models.Model):# ????foreign = models.ForeignKey(A, on_delete=models.CASCADE) ?# 删除级联# ????# foreign = models.ForeignKey(A, on_delete=models.PROTECT)# ????# foreign = models.ForeignKey(A, on_delete=models.SET_NULL, null=True, blank=True) ?# 删除置空# ????# foreign = models.ForeignKey(A, on_delete=models.SET_DEFAULT, default=0)# ????# foreign = models.ForeignKey(A, on_delete=models.DO_NOTHING)# ????# foreign = models.ForeignKey(A, on_delete=models.SET)### class C(models.Model):# ????manytomany = models.ManyToManyField(B)# 1.所有字段都有的参数# 2.个别字段才有的参数# 3.关系型字段的参数"""on_delete 当一个被外键关联的对象被删除时，Django将模仿on_delete参数定义的SQL约束执行相应操作 ???如下6种操作 ???CASCADE：模拟SQL语言中的ON DELETE CASCADE约束，将定义有外键的模型对象同时删除！（该操作为当前Django版本的默认操作！） ???PROTECT:阻止上面的删除操作，但是弹出ProtectedError异常 ???SET_NULL：将外键字段设为null，只有当字段设置了null=True时，方可使用该值。 ???SET_DEFAULT:将外键字段设为默认值。只有当字段设置了default参数时，方可使用。 ???DO_NOTHING：什么也不做。 ???SET()：设置为一个传递给SET()的值或者一个回调函数的返回值。注意大小写。"""

from django.db import models# Create your models here.class AddressInfo(models.Model): ?# coures_addressinfo ???"""省市县地址信息""" ???address = models.CharField(max_length=200, null=True, blank=True, verbose_name="地址") ???pid = models.ForeignKey(‘self‘, null=True, blank=True, verbose_name="自关联",on_delete=models.SET_NULL) ???# pid = models.ForeignKey(‘AddressInfo‘, null=True, blank=True, verbose_name="自关联") ???note = models.CharField(max_length=200, null=True, blank=True, verbose_name="说明") ???def __str__(self): ?# __unicode__(self) ???????return self.address ???class Meta: ???????# 定义元数据 ???????db_table = ‘address‘ ???????# ordering = [‘pid‘] ?# 指定按照什么字段排序 ???????verbose_name = ‘省市县地址信息‘ ???????verbose_name_plural = verbose_name ???????# abstract = True ???????# permissions = ((‘定义好的权限‘, ‘权限说明‘),) ???????# managed = False ???????unique_together = (‘address‘, ‘note‘) ?# ((),()) ???????# app_label = ‘courses‘ ???????# db_tablespace ?# 定义数据库表空间的名字class Teacher(models.Model): ???"""讲师信息表""" ???nickname = models.CharField(max_length=30, primary_key=True, db_index=True, verbose_name="昵称") ???introduction = models.TextField(default="这位同学很懒，木有签名的说~", verbose_name="简介") ???fans = models.PositiveIntegerField(default="0", verbose_name="粉丝数") ???created_at = models.DateTimeField(auto_now_add=True, verbose_name="创建时间") ???updated_at = models.DateTimeField(auto_now=True, verbose_name="更新时间") ???class Meta: ???????verbose_name = "讲师信息表" ???????verbose_name_plural = verbose_name ???def __str__(self): ?# Python2:__unicode__ ???????return self.nicknameclass Course(models.Model): ???"""课程信息表""" ???title = models.CharField(max_length=100, primary_key=True, db_index=True, verbose_name="课程名") ???teacher = models.ForeignKey(Teacher, null=True, blank=True, on_delete=models.CASCADE, ???????????????????????????????verbose_name="课程讲师") ?# 删除级联 ???type = models.CharField(choices=((1, "实战课"), (2, "免费课"), (0, "其它")), max_length=12, ???????????????????????????default=0, verbose_name="课程类型") ???price = models.PositiveSmallIntegerField(verbose_name="价格") ???volume = models.BigIntegerField(verbose_name="销量") ???online = models.DateField(verbose_name="上线时间") ???created_at = models.DateTimeField(auto_now_add=True, verbose_name="创建时间") ???updated_at = models.DateTimeField(auto_now=True, verbose_name="更新时间") ???class Meta: ???????verbose_name = "课程信息表" ???????get_latest_by = "created_at" ???????verbose_name_plural = verbose_name ???def __str__(self): ???????return f"{self.get_type_display()}-{self.title}" ?# 示例：实战课-Django零基础入门到实战 ???????# return "{}-{}".format(self.get_type_display(), self.title) ?# 示例：实战课-Django零基础入门到实战class Student(models.Model): ???"""学生信息表""" ???nickname = models.CharField(max_length=30, primary_key=True, db_index=True, verbose_name="昵称") ???course = models.ManyToManyField(Course, verbose_name="课程") ???age = models.PositiveSmallIntegerField(verbose_name="年龄") ???gender = models.CharField(choices=((1, "男"), (2, "女"), (0, "保密")), max_length=1, ?????????????????????????????default=0, verbose_name="性别") ???study_time = models.PositiveIntegerField(default="0", verbose_name="学习时长(h)") ???created_at = models.DateTimeField(auto_now_add=True, verbose_name="创建时间") ???updated_at = models.DateTimeField(auto_now=True, verbose_name="更新时间") ???class Meta: ???????verbose_name = "学生信息表" ???????ordering = [‘age‘] ???????verbose_name_plural = verbose_name ???def __str__(self): ???????return self.nicknameclass TeacherAssistant(models.Model): ???"""助教信息表""" ???nickname = models.CharField(max_length=30, primary_key=True, db_index=True, verbose_name="昵称") ???teacher = models.OneToOneField(Teacher, null=True, blank=True, on_delete=models.SET_NULL, ??????????????????????????????????verbose_name="讲师") ?# 删除置空 ???hobby = models.CharField(max_length=100, null=True, blank=True, verbose_name="爱好") ???created_at = models.DateTimeField(auto_now_add=True, verbose_name="创建时间") ???updated_at = models.DateTimeField(auto_now=True, verbose_name="更新时间") ???class Meta: ???????verbose_name = "助教信息表" ???????db_table = "courses_assistant" ???????verbose_name_plural = verbose_name ???def __str__(self): ???????return self.nickname

 # # 1.查询、检索、过滤 ???????# teachers = Teacher.objects.all() ???????# print(teachers) ???????# teacher2 = Teacher.objects.get(nickname=‘Jack‘) ?# get()只能返回一条结果，多条则会报错 ???????# print(teacher2, type(teacher2)) ???????# teacher3 = Teacher.objects.filter(fans__gte=500) ?# QuerySet, 可以是多条结果 ???????# for t in teacher3: ???????# ????print(f"讲师姓名{t.nickname}--粉丝数{t.fans}") ???????# # 2.字段数据匹配，大小写敏感 ???????# teacher4 = Teacher.objects.filter(fans__in=[666, 1231]) ???????# print(teacher4) ???????# teacher5 = Teacher.objects.filter(nickname__icontains=‘A‘) ???????# print(teacher5) ???????# # 3.结果切片、排序、链式查询 ???????# print(Teacher.objects.all()[:1]) ???????# teacher6 = Teacher.objects.all().order_by(‘-fans‘) ???????# for t in teacher6: ???????# ????print(t.fans) ???????# print(Teacher.objects.filter(fans__gte=500).order_by(‘nickname‘)) ???????# # 4.查看执行的原生SQL ???????# print(str(Teacher.objects.filter(fans__gte=500).order_by(‘nickname‘).query)) ???????# """SELECT `courses_teacher`.`nickname`, `courses_teacher`.`introduction`, `courses_teacher`.`fans`, ???????# `courses_teacher`.`created_at`, `courses_teacher`.`updated_at` FROM `courses_teacher` ???????# WHERE `courses_teacher`.`fans` >= 500 ORDER BY `courses_teacher`.`nickname` ASC ???????# """ ???????"""返回新QuerySet API""" ???????# 1.all(), filter(), order_by(), exclude(), reverse(), distinct() ???????# s1 = Student.objects.all().exclude(nickname=‘A同学‘) ???????# for s in s1: ???????# ????print(s.nickname, s.age) ???????# s2 = Student.objects.all().exclude(nickname=‘A同学‘).reverse() ???????# for s in s2: ???????# ????print(s.nickname, s.age) ???????# 2.extra(), defer(), only() 实现字段别名，排除一些字段，选择一些字段 ???????# s3 = Student.objects.all().extra(select={"name": "nickname"}) ???????# for s in s3: ???????# ????print(s.name) ???????# print(str(Student.objects.all().only(‘nickname‘, ‘age‘).query)) ???????# 3.values(), values_list() 获取字典或元组形式的QuerySet ???????# print(TeacherAssistant.objects.values(‘nickname‘, ‘hobby‘)) ???????# print(TeacherAssistant.objects.values_list(‘nickname‘, ‘hobby‘)) ???????# print(TeacherAssistant.objects.values_list(‘nickname‘, flat=True)) ???????# 4.dates(), datetimes() ?根据时间日期获取查询集 ???????# print(Course.objects.dates(‘created_at‘, ‘year‘, order=‘DESC‘)) ???????# print(Course.objects.datetimes(‘created_at‘, ‘year‘, order=‘DESC‘)) ???????# 5.union(), intersection(), difference() 并集、交集、差集 ???????# p_240 = Course.objects.filter(price__gte=240) ???????# p_260 = Course.objects.filter(price__lte=260) ???????# print(p_240.union(p_260)) ???????# print(p_240.intersection(p_260)) ???????# print(p_240.difference(p_260)) ???????# 6.select_related() 一对一、多对一查询优化, prefetch_related() 一对多、多对多查询优化；反向查询 ???????# courses = Course.objects.all().select_related(‘teacher‘) ???????# for c in courses: ???????# ????print(f"{c.title}--{c.teacher.nickname}--{c.teacher.fans}") ???????# students = Student.objects.filter(age__lt=30).prefetch_related(‘course‘) ???????# for s in students: ???????# ????print(s.course.all()) ???????# print(Teacher.objects.get(nickname="Jack").course_set.all()) ???????# 7.annotate() 使用聚合计数、求和、平均数 raw() 执行原生的SQL ???????# print(Course.objects.values(‘teacher‘).annotate(vol=Sum(‘volume‘))) ???????# print(Course.objects.values(‘teacher‘).annotate(pri=Avg(‘price‘))) ???????# """不返回Query API""" ???????# # 1.获取对象 get(), get_or_create(), first(), last(), latest(), earliest(), in_bulk() ???????# print(Course.objects.first()) ???????# print(Course.objects.last()) ???????# print(Course.objects.earliest()) ???????# print(Course.objects.latest()) ???????# print(Course.objects.in_bulk([‘Python系列教程4‘, ‘Golang系列教程1‘])) ???????# ???????# # 2.创建对象 create(), bulk_create(), update_or_create() 创建，批量创建，创建或更新 ???????# ???????# # 3.更新对象 update(), update_or_create() 更新，更新或创建 ???????# Course.objects.filter(title=‘Java系列教程2‘).update(price=300) ???????# ???????# # 4.删除对象 delete() 使用filter过滤 ???????# Course.objects.filter(title=‘test‘).delete() ???????# ???????# # 5.其它操作 exists(), count(), aggregate() 判断是否存在，统计个数，聚合 ???????# print(Course.objects.filter(title=‘test‘).exists()) ???????# print(Course.objects.filter(title=‘Java系列教程2‘).exists()) ???????# print(Course.objects.count()) ???????# print(Course.objects.aggregate(Max(‘price‘), Min(‘price‘), Avg(‘price‘), Sum(‘volume‘))) ???????# courses = Course.objects.values(‘teacher‘).annotate(t=GroupConcat(‘title‘, distinct=True, ???????# ??????????????????????????????????????????????????????????????????ordering=‘title ASC‘, ???????# ??????????????????????????????????????????????????????????????????separator=‘-‘)) ???????# for c in courses: ???????# ????print(c) ???????# Course.objects.update(price=F(‘price‘) - 11) ???????# print(Course.objects.filter(volume__lte=F(‘price‘) * 10)) ???????# ???????# print(Course.objects.filter(Q(title__icontains=‘java‘) & Q(volume__gte=5000))) ???????# ???????# print(Course.objects.filter(Q(title__icontains=‘golang‘) | Q(volume__lte=1000)))