django模型篇：一對一、一對多、多對多，添加，批量插入和查詢操作

模型類

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)

一對多和多對多 添加操作

# 一對多添加用戶
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  )
# 多對多添加用戶
author01 = Author.objects.get(id="1") 
author02 = Author.objects.get(id="2")
 book = Book.objects.get(nid='2')
# book.authors.add(author01, author02)
# 多對多第二種 
book.authors.add(1, 2)
# 多對多第三種
book.authors.add(*[1, 2])
# 刪除關聯的作者
 book.authors.remove(author01)
# 刪除所有關聯的作者
 book.authors.clear() 
# 先刪除所有在綁定
book.authors.set(1)

查詢操作

基於對象的跨表查詢（基於子查詢）

# 一對多查詢
    # 正查
    book = Book.objects.get(nid='1')
    # 取到關聯的對象
    publish = book.publish_id
    print(publish.name)

    # 反查
    publish = Publish.objects.get(nid='1')
    books = publish.book_set.all()

    # 多對多查詢
    book = Book.objects.get(nid='1')
    authors = book.authors.all()

    author = Author.objects.get(id='1')
    book = author.book_set.all()

    # 一對一
    author = Author.objects.get(id='1')
    ad = author.ad
    author_detail = AuthorDetail.objects.get(id='1')
    author = author_detail.author

# 基於雙下划線的跨表查詢（基於join實現的）
# KEY：正向查詢按字段，反向查詢按表明小寫

# linux這本書的出版社名字
    # 正向
    name = Book.objects.filter(title='linux').values('publish_id__name')
    # 反向
    name = Publish.objects.filter(book__title='linux').values('name')

    # 查詢第一個出版社對用的所有書
    # 正向
    book = Publish.objects.filter(nid='1').values('book__title')
    # 反向
    book = Book.objects.filter(publish_id_id='1').values('title')

    # 查詢Linux這本書所有作者的手機號
    telephone = Book.objects.filter(title='linux').values('authors__ad__telephone')
    telephone = Author.objects.filter(book__title='linux').values('ad__telephone')

    # 查詢id=1的出版社的作者的書籍和作者的名字
    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')

    # 查詢作者手機號的開頭為110的書籍和出版社名稱
    title_name = Author.objects.filter(ad__address__startswith='北京').values('book__title', 'book__publish_id__name')

# 聚合和分組

from django.db.models import Avg, Max, Sum, Min, Count
    avg = Book.objects.all().aggregate(price=Avg('price'))

    # 單表分組查詢
    # 查詢每個出版社id以及對應大的書籍個數
    count = Book.objects.values('publish_id').annotate(count=Count(1))

    # values中的值為分類的參數
    '''
        select Count(1) from Book GROUP by publish_id
    '''
    # 跨表分組查詢
    # 查看每一個出版社名稱以及對應的書籍個數
    count = Book.objects.values('publish_id__name').annotate(count=Count(1))
    count = Publish.objects.values('name').annotate(c=Count('book__nid'))
    # 查找作者大於一個的書籍對應的作者數
    query = Book.objects.annotate(c=Count('authors')).filter(c__gt=1).values('c', 'title')

 轉載自：https://www.cnblogs.com/ls1997/p/10970583.html