ORM多表分组F与Q查询

Posted 2020-12-03 yaya625202

编辑本博客

一、分组查询

先连接表，再分组查询

需求：查询每一个出版社出版的名称以及书籍个数

SQL连接表：

SELECT * FROM app_book INNER JOIN app_publish on app_book.publish_id = app_publish.nid

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ORM连接表：

Book.objects.values("publish").values()

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SQL链表后分组：

SELECT count(title),app_publish.name FROM app_book INNER JOIN app_publish on app_book.publish_id = app_publish.nid GROUP BY publish_id

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ORM链表后分组，方式一：

Publish.objects.values("name").annotate(Count("book__title"))

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ORM链表后分组，方式二：

通过values拿所需数据即可

Publish.objects.values("nid").annotate(c=Count("book__title")).values(‘name‘,"c")

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练习二：

查询每一个作者的名字以及出版过的书籍的最高价格

SQL语法：

SELECT app_author.name,max(price) FROM app_author INNER JOIN app_book_authors ON app_author.nid = app_book_authors.author_id INNER JOIN app_book ON app_book_authors.book_id = app_book.nid ORDER BY app_author.nid

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ORM操作：