django ORM 查询关系

模型关系:

from django.db import models
# Create your models here.
class Author(models.Model):
 nid = models.AutoField(primary_key=True)
 name = models.CharField(max_length=32)
 age = models.IntegerField()
 # 与AuthorDetail建立一对一的关系
 authorDetail = models.OneToOneField(to="AuthorDetail", on_delete=models.CASCADE)
class AuthorDetail(models.Model):
 nid = models.AutoField(primary_key=True)
 birthday = models.DateField()
 telephone = models.BigIntegerField()
 addr = models.CharField(max_length=64)
class Publish(models.Model):
 nid = models.AutoField(primary_key=True)
 name = models.CharField(max_length=32)
 city = models.CharField(max_length=32)
 email = models.EmailField()
class Book(models.Model):
 nid = models.AutoField(primary_key=True)
 title = models.CharField(max_length=32)
 publishDate = models.DateField()
 price = models.DecimalField(max_digits=5, decimal_places=2)
 # 与Publish建立一对多的关系,外键字段建立在多的一方
 publish = models.ForeignKey(to="Publish", to_field="nid", on_delete=models.CASCADE)
 # 与Author表建立多对多的关系,ManyToManyField可以建在两个模型中的任意一个,自动创建第三张表
 authors = models.ManyToManyField(to='Author', )

1.查询python这本书籍的出版社的邮箱

 # 正向查询按字段
 v = models.Book.objects.filter(title="python教程").first()
 print(v.publish.email)
 # beijing@163.com

2. 反向查询按 表名小写_set.all()

 # 海南出版社出版的书籍名称
 # filter 和 get 区别, filter 查出来是集合,所以经常跟first(), get 查出来是对象。
 v = models.Publish.objects.filter(name='海南出版社').first()
 # v = models.Publish.objects.get(name='海南出版社')
 for book in v.book_set.all():
 print(book.title)
# golang教程
 #nodejs 教程

3.查询golang作者的年龄

 # 按字段(authors.all())
 # 多对多 book -----------------------> author
 # <----------------
 # book_set.all()
ath = models.Book.objects.filter(title="golang教程").first()
 for auther in ath.authors.all():
 print(auther.name, auther.age)
# 小明 10
# 莉君 12

4.查询莉君出版过的书籍名称

ath = models.Author.objects.filter(name='莉君').first()
 for book in ath.book_set.all():
 print(book.title)
# golang教程
# nodejs 教程

5. 查询莉君的手机号

 ath = models.Author.objects.filter(name='莉君').first()
 print(ath.authorDetail.telephone)
# 18938641414

6. 查询家在深圳的作者名字

 dais = models.AuthorDetail.objects.filter(addr='深圳市')
 for ath in dais:
 print(ath.author.name)
# 莉君

6. 北京出版社出版的书籍名称

 ret1 = models.Publish.objects.filter(name="成都出版社").values('book__title')
 print(ret1.query)
 '''
 SELECT `app01_book`.`title` FROM `app01_publish` 
 LEFT OUTER JOIN `app01_book`
 ON (`app01_publish`.`nid` = `app01_book`.`publish_id`) WHERE `app01_publish`.`name` = 成都出版社
 '''
 # 方式2:
 ret2 = models.Book.objects.filter(publish__name="成都出版社").values("title")
 print(ret2.query)
 """
 SELECT `app01_book`.`title` FROM `app01_book`
 INNER JOIN `app01_publish` 
 ON (`app01_book`.`publish_id` = `app01_publish`.`nid`) WHERE `app01_publish`.`name` = 成都出版社
 """

7.查询手机号以188开头的作者出版过的书籍名称以及书籍对应的出版社名称

 # ret3 = models.Book.objects.filter(authors__authorDetail__telephone__startswith="188").values('title', 'publish__name')
 #
 # print(ret3.query)
 """
 SELECT `app01_book`.`title`, `app01_publish`.`name` FROM `app01_book`
 INNER JOIN `app01_book_authors` ON (`app01_book`.`nid` = `app01_book_authors`.`book_id`)
 INNER JOIN `app01_author` ON (`app01_book_authors`.`author_id` = `app01_author`.`nid`) 
 INNER JOIN `app01_authordetail` ON (`app01_author`.`authorDetail_id` = `app01_authordetail`.`nid`) 
 INNER JOIN `app01_publish` ON (`app01_book`.`publish_id` = `app01_publish`.`nid`) 
 WHERE `app01_authordetail`.`telephone` LIKE BINARY 188%
 """

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