“子查询返回多于 1 行"错误. [英] "subquery returns more than 1 row" error.

问题描述

我是网络编程的新手，我正在尝试制作 twitter 克隆.此时，我有 3 个表:

I am new to web programming and I'm trying to make a twitter-clone. At this point, I have 3 tables:

用户(ID，姓名)

• id 是自动生成的 id
• 用户名

推文(id、内容、user_id)

tweets (id, content, user_id)

• id 是自动生成的 id
• content 是推文的文本
• user_id 是发布帖子的用户的 ID

关注者(id、user_id、follow_id)

followers (id, user_id, following_id)

• id 是自动生成的 id
• user_id 是执行以下操作的用户
• following_id 是被关注的用户

因此，作为 sql 的新手，我正在尝试构建一个 SQL 语句，该语句将返回当前登录用户及其关注的每个人的推文.

So, being new to sql as well, I am trying to build an SQL statement that would return the tweets that the currently-logged in user and of everyone he follows.

我尝试使用此语句，该语句有时有效，但有时，我收到一条错误消息，指出子查询返回多于 1 行".声明如下:

I tried to use this statement, which works sometimes, but other times, I get an error that says "Subquery returns more than 1 row". Here is the statement:

SELECT * FROM tweets 
WHERE user_id IN
((SELECT following_id FROM followers
WHERE user_id = 1),1) ORDER BY date DESC

• 我在这里以 1 为例，这将是当前登录用户的 id.

我对这个声明没有任何运气；任何帮助将不胜感激！谢谢.

I haven't had any luck with this statement; any help would be greatly appreciated! Thank you.

推荐答案

SELECT * 
FROM tweets 
WHERE 
  user_id IN (SELECT following_id FROM followers WHERE user_id = 1)
  OR user_id = 1
ORDER BY date DESC

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