django orm 基本
1 modle基本数据类型
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
class Test(models.Model): """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) 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()
2 modle的 外键
主要有三类: 一对一 models.OneToOneField (如一个表字段太多,有些字段平时不怎们用到,可利用外键将其另建表关联) ,一对多 models.ForeignKey ( 如老师对课程 ) , 多对多 models.ManyToManyField ( 如学生对课程 )
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
class A(models.Model): onetoone = models.OneToOneField(Test, related_name="one") 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) #外键删除之后设置默认值,必须设置默认值 foreign = models.ForeignKey(A, on_delete=models.DO_NOTHING) #什么也不做 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。 """
补充:自关联时,传入的类名为self,
pid = models.ForeignKey('self', null=True, blank=True, verbose_name="自关联")
3 modle 的 元数据Meta
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
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") # 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
补充
1 也可以在modle类中自定义函数 可以调用这些函数方法实现一些功能,如用在template模板中调用这些方法。
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
class Teacher(models.Model): ...... def __str__(self): # Python2:__unicode__ return f'Teacher : {self.nickname}' def get_course_num(self): """获取课程数""" return self.Course_set.all().count() class Course(models.Model): """课程信息表""" teacher = models.ForeignKey(Teacher, null=True, blank=True, on_delete=models.CASCADE, verbose_name="课程讲师") # 删除级联
· 在html模板中调用此函数 {{ teacher.get_course_num }}
2 对于一些字段 里面采用choice 来规定存储值范围的的调用,如:
degree = models.CharField(max_length=7, choices=(('primary', '初级'), ('midd', '中级'), ('high', '高级')), verbose_name='课程难度')
数据库中的值限定在 ('primary', 'midd', 'high') 之中,我们希望显示为 ( '初级', '中级', '高级' ) 可以采用 {{ course.get_degree_display }}
4 利用modle对数据库进行操作:
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
from django.db.models import Count, Avg, Max, Min, Sum, F, Q from django.views.generic import View class IndexView(View): """主页""" def get(self, request): # # 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)) # 结果为: """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)))
5 django 的modle不经可以在django view这些地方操作,也可以调用此modle对数据库进行操作,如不用写 sql 语句而使用相关 modle类 对数据库数据实现导入导出修改查找等操作(即orm),
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
import os import sys import random import django from datetime import date project_path = os.path.dirname(os.path.dirname(os.path.abspath(__file__))) sys.path.append(project_path) # 将项目路径添加到系统搜寻路径当中 os.environ['DJANGO_SETTINGS_MODULE'] = 'imooc.settings' # 设置项目的配置文件 django.setup() from courses.models import Teacher, Course, Student, TeacherAssistant def import_data(): """使用Django ORM导入数据""" # 讲师数据 create() Teacher.objects.create(nickname="Jack", introduction="Python工程师", fans=666) # 课程数据 bulk_create() Course.objects.bulk_create([Course(title=f"Python系列教程{i}", teacher=Teacher.objects.get(nickname="Jack"), type=random.choice((0, 1, 2)), price=random.randint(200, 300), volume=random.randint(100, 10000), online=date(2018, 10, 1)) for i in range(1, 5)]) # 学生数据 update_or_create() Student.objects.update_or_create(nickname="A同学", defaults={"age": random.randint(18, 58), "gender": random.choice((0, 1, 2)), "study_time": random.randint(9, 999)}) # 正向添加 # 销量大于等于1000的课程 Student.objects.get(nickname="A同学").course.add(*Course.objects.filter(volume__gte=1000)) # 反向添加 # 学习时间大于等于500小时的同学 Course.objects.get(title="Python系列教程1").student_set.add(*Student.objects.filter(study_time__gte=500)) # 助教数据 get_or_create() TeacherAssistant.objects.get_or_create(nickname="助教1", defaults={"hobby": "慕课网学习", "teacher": Teacher.objects.get(nickname="Jack")}) return True if __name__ == "__main__": if import_data(): print("数据导入成功!")
注: 导入modle 类必须在 django.setup() 之后导入,否则找不到路径
注: 主要参考 慕课网课程 全面掌握Django ORM https://www.imooc.com/learn/1087