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')
