Question

对不起，如果标题与我的问题无关。我不知道这个正确的标题是什么。

所以我有5个表格，以便向用户显示相关内容

内容（id，内容等）。Data related content
ContentCategory（id，contentId，followCategoryId）Data related content's categories
ContentPublisher（id，contentId，followPublisherId）Data related content's publishers
FollowCategory（id，categoryId，userId（关注的人）等。）Data related user's followed categories
FollowPublisher（id，publisherId，userId（关注的人）等）。Data related user's followed publishers

如何根据用户的关注类别和关注的发布者显示内容，以及如果可能的话，如何区分内容是否来自followCategory或followPublisher上的关系

例如：以下是我的查询，用于显示基于用户FollowPublisher cmiiw的内容

SELECT content.id, content.description, ...etc 
FROM followPublisher
LEFT JOIN publisher ON followPublisher.publisherId = publisher.id
LEFT JOIN contentPublisher ON publisher.id = contentPublisher.publisherId
RIGHT JOIN content ON contentPublisher.contentId = content.id
    WHERE followPublisher.userId = 8
ORDER BY content.created desc;

以下是我的查询，用于根据用户的关注类别显示内容

SELECT content.id, content.description, ...etc 
FROM followCategory
LEFT JOIN category ON followCategory.categoryId = category.id
LEFT JOIN contentCategory ON category.id = contentCategory.categoryId
RIGHT JOIN content ON contentCategory.contentId = content.id
    WHERE followCategory.userId = 8
ORDER BY content.created desc;

如何结合这两个查询以一次基于用户的关注类别和发布者显示内容，或者有没有比合并查询更好的方法了？

Answer 1

我认为您需要以下条件：

from pprint import pprint

def fib(n):
    if n == 0 or n == 1:
        return 1

    pprint(f" fib({n - 1})")  # f" fib({fib(n - 1)})"
    pprint(f" fib({n - 2})")
    fib(n - 1) + fib(n - 2)

    return fib(n - 1) + fib(n - 2)


fib(5)

Answer 2

使用联盟

有2个条件

不要在order by中使用任何与表相关的信息（以idk的说法表示），而应使用as重命名。在我的情况下，order by content.created应该更改为content.created as contentCreated，然后我们可以使用它order by。
添加默认值列以指示数据的来源（在这种情况下，数据来自followPublisher还是followCategory）

查询：

SELECT content.id, content.description, content.created as contentCreated ...etc, 'publisher' as type
FROM followPublisher
LEFT JOIN publisher ON followPublisher.publisherId = publisher.id
LEFT JOIN contentPublisher ON publisher.id = contentPublisher.publisherId
RIGHT JOIN content ON contentPublisher.contentId = content.id
    WHERE followPublisher.userId = 8
UNION
SELECT content.id, content.description, content.created as contentCreated ...etc, 'category' as type
FROM followCategory
LEFT JOIN category ON followCategory.categoryId = category.id
LEFT JOIN contentCategory ON category.id = contentCategory.categoryId
RIGHT JOIN content ON contentCategory.contentId = content.id
    WHERE followCategory.userId = 8
ORDER BY contentCreated desc;

sql-查询连接2个表和1个表

2 个答案: