day057 基于对象和基于双下划线的多表查询

太过爱你忘了你带给我的痛 2022-01-07 12:25 167阅读 0赞

**单表查询和多表查询的添加与查询**

**![1547030-20190302150955770-1548051605.png][]    ![1547030-20190302151010871-1603740050.png][]    ![1547030-20190302151029382-1182333041.png][]  **![1547030-20190302151122876-1997547656.png][]       ![1547030-20190302151515856-1962665024.png][]

**上述关系:author-authordetail是一对一的关系(外键在author上名为authors),  book-publish是一对多的关系(外键在book上名为publisher), book-author是多对多的关系(外键在book上名为books),** **其中book和author是通过第三张表book\_author建立的关系.**

**1.查询**

**一对一查询:(onetoonefield(to=与那个表进行关联,to\_field=与那个字段进行关联)) **

设置级联删除(to\_delete=models.CASCADE)

正向查询:   查询小可爱的电话号码

models.author.objects.filter(name='小可爱').authors.tel

models.author.objects.filter(name='小可爱').values(authors__tel)

反向查询: 查询电话号码为443355的作者姓名

models.authordetail.objects.filter(tel='443355').author.name

models.authordetail.objects.filter(authors\_\_tel=443355).values(name)

**一对多查询:(foreignkey(to=与那个表进行关联))**

正向查询: 查询书名为三国演义的出版社的地址

models.book.objects.filter(title='三国演义').publisher.addr

models.book.objects.filter(title='三国演义').values(publisher\_\_addr)

反向查询: 查询山东大学出版社出版的书的价格

models.publish.objects.filter(name='山东大学出版社').book_set.all().values(price)

models.publish.objects.filter(publisher\_\_name='山东大学出版社').values(price)

**多对多查询:( manytomanyfield(to=与那个表进行关联) )**

正向查询: 查询天龙八部的作者

models.book.objects.filter(title='天龙八部').authors.all().values(name)

models.book.objects.filter(title='天龙八部').values(authors\_\_name)

反向查询: 查询彭于晏出过的书

models.author.objects.filter(name='彭于晏').books_set.all().values(title)

models.book.objects.filter(authors\_\_name='彭于晏').values(title)

转载于:https://www.cnblogs.com/zty1304368100/p/10461187.html

[1547030-20190302150955770-1548051605.png]: https://img2018.cnblogs.com/blog/1547030/201903/1547030-20190302150955770-1548051605.png
[1547030-20190302151010871-1603740050.png]: https://img2018.cnblogs.com/blog/1547030/201903/1547030-20190302151010871-1603740050.png
[1547030-20190302151029382-1182333041.png]: https://img2018.cnblogs.com/blog/1547030/201903/1547030-20190302151029382-1182333041.png
[1547030-20190302151122876-1997547656.png]: https://img2018.cnblogs.com/blog/1547030/201903/1547030-20190302151122876-1997547656.png
[1547030-20190302151515856-1962665024.png]: /images/20211220/d41ceb6643a44e9f9b0fcd3c5148ecaa.png