Django模型类之models字段类型和参数以及元数据meta
models之字段类型和参数
示例:
# 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。 """
实际创建表单示例:
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.nickname class 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.nickname class 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
简单查询语句等
# # 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)))
