在mysql中内部联接多个表

问题描述

我的数据库中有三个表用户，帖子和评论.

I Have three tables in my databaseusers , posts and comments.

它们的结构如下:

**users** :
user_id , user_name
**posts**:
post_id , post_content, user_id
**comments** :
comment_id , comment_content , post_id, user_id

现在我想以以下方式使用join从这三个表中获取数据:comment_id，comment_content，user_id，user_name，post_id谁能告诉我该怎么做?我应该非常感谢.

now i want to fetch data from these three tables using join in a following way :comment_id, comment_content, user_id, user_name, post_idcan anyone plz tell me that how this can be done ?I Shall be very thankful.

推荐答案

这是一个简单的JOIN.

尝试一下:

select c.comment_id,
    c.comment_content,
    u.user_id,
    u.user_name,
    c.post_id
from comments c
join users u on u.user_id = c.user_id;

如果您还需要发件表中的列，请加入它:

If you need columns from posts table too, join it:

select c.comment_id,
    c.comment_content,
    u.user_id,
    u.user_name,
    p.post_id,
    p.post_content
from comments c
join users u on u.user_id = c.user_id
join posts p on c.post_id = p.post_id;

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