Django ORM 一对一,一对多,多对多, 添加,批量插入和查询 F与Q添加

模型类

class Book(models.Model): nid = models.AutoField(primary_key=True) title = models.CharField(max_length=32, default=None) create_time = models.DateTimeField() price = models.DecimalField(decimal_places=2, max_digits=8, default=None) publish_id = models.ForeignKey(to="Publish", on_delete=models.CASCADE) authors = models.ManyToManyField(to='Author') def __str__(self): return str(self.nid) + ':' + self.title class Publish(models.Model): nid = models.AutoField(primary_key=True) name = models.CharField(max_length=32) email = models.CharField(max_length=32) class Author(models.Model): name = models.CharField(max_length=32) age = models.IntegerField() email = models.CharField(max_length=32) ad = models.OneToOneField(to="AuthorDetail", on_delete=models.CASCADE) class AuthorDetail(models.Model): address = models.CharField(max_length=32) telephone = models.IntegerField()

批量插入

book_list = [] for i in range(100): book = Book(title='book_%s' % i, price=i * i) book_list.append(book) Book.objects.bulk_create(book_list)

 

一对多和多对多 添加操作

# 一对多添加用户

publish = Publish.objects.get(nid=1)

Book.objects.create(

  title='ubuntu',

  price=122,

  create_time='2012-2-2',

  publish_id=publish,

  # publish_id_id=publish.nid )

# 多对多添加用户

author01 = Author.objects.get(id="1")

author02 = Author.objects.get(id="2")

book = Book.objects.get(nid='2')

# book.authors.add(author01, author02)

# 多对多第二种 

book.authors.add(1, 2)

# 多对多第三种

book.authors.add(*[1, 2])

# 删除关联的作者

book.authors.remove(author01)

# 删除所有关联的作者

book.authors.clear()

# 先删除所有在绑定

book.authors.set(1)

查询操作

基于对象的跨表查询（基于子查询）

    # 一对多查询
    # 正查
    book = Book.objects.get(nid='1') # 取到关联的对象
    publish = book.publish_id print(publish.name) # 反查
    publish = Publish.objects.get(nid='1') books = publish.book_set.all() # 多对多查询
    book = Book.objects.get(nid='1') authors = book.authors.all() author = Author.objects.get(id='1') book = author.book_set.all() # 一对一
    author = Author.objects.get(id='1') ad = author.ad author_detail = AuthorDetail.objects.get(id='1') author = author_detail.author

# 基于双下划线的跨表查询（基于join实现的）
# KEY：正向查询按字段，反向查询按表明小写

    # linux这本书的出版社名字
    # 正向
    name = Book.objects.filter(title='linux').values('publish_id__name') # 反向
    name = Publish.objects.filter(book__title='linux').values('name') # 查询第一个出版社对用的所有书
    # 正向
    book = Publish.objects.filter(nid='1').values('book__title') # 反向
    book = Book.objects.filter(publish_id_id='1').values('title') # 查询Linux这本书所有作者的手机号
    telephone = Book.objects.filter(title='linux').values('authors__ad__telephone') telephone = Author.objects.filter(book__title='linux').values('ad__telephone') # 查询id=1的出版社的作者的书籍和作者的名字
    title_name = Publish.objects.filter(nid='1').values('book__authors__name', 'book__title') title_name = Book.objects.filter(publish_id_id=1).values('title', 'authors__name') # 查询作者手机号的开头为110的书籍和出版社名称
    title_name = Author.objects.filter(ad__address__startswith='北京').values('book__title', 'book__publish_id__name')

# 聚合和分组

 from django.db.models import Avg, Max, Sum, Min, Count avg = Book.objects.all().aggregate(price=Avg('price')) # 单表分组查询 # 查询每个出版社id以及对应大的书籍个数 count = Book.objects.values('publish_id').annotate(count=Count(1)) # values中的值为分类的参数 ''' select Count(1) from Book GROUP by publish_id ''' # 跨表分组查询 # 查看每一个出版社名称以及对应的书籍个数 count = Book.objects.values('publish_id__name').annotate(count=Count(1)) count = Publish.objects.values('name').annotate(c=Count('book__nid')) # 查找作者大于一个的书籍对应的作者数 query = Book.objects.annotate(c=Count('authors')).filter(c__gt=1).values('c', 'title')

 

F与Q

F 比较两列大小

Q 两个关系用 与或非 表示

  # F与Q查询
    from django.db.models import F, Q # 查询评论数大于点赞数的书籍名称 title = Book.objects.filter(commit_count__gt=F('poll_count') * 1).values('title') # 让所有的书籍价格加100 price = Book.objects.update(price=F('price') + 100) # 取出评论大于20或者点赞数小于10 ret = Book.objects.filter(Q(commit_count__gt=20) | ~Q(poll_count__gt=10)) # 取价格在等于20或者评论数大于20且点赞数小于10的 ret = Book.objects.filter(Q(Q(price=20) | Q(commit_count__gt=20)) & ~Q(poll_count__gt=10)) ret = Book.objects.filter(Q(Q(price=20) | Q(commit_count__gt=20)), ~Q(poll_count__gt=10))

 

Q的添加操作

q = Q() #添加的元素关系为或 q.connertor ="or" #添加查询条件 q.children.append(("name","123")) q.children.append("age","12")