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  • 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")
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  • 原文地址:https://www.cnblogs.com/ls1997/p/10970583.html
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