将同一张表在不同的列上连接两次 [英] joining the same table twice on different columns

问题描述

我有一个user表和一个complaint表.

complaint表具有以下结构:

[opened_by]   [complaint_text]   [closed_by]
 (user_id)         (text)         (user_id)
 (user_id)         (text)         (user_id)
 (user_id)         (text)         (user_id)

所有用户，投诉人和投诉投诉人都位于表user中.

All users, both the complainers and complaint-resolvers are located in table user.

如何编写查询以显示两列的用户名?

How do I write a query to show the username for both columns?

这给了我一个:

SELECT user.username, complaint.complaint_text
FROM complaint
LEFT JOIN user ON user.user_id=complaint.opened_by

但是我不知道怎么写，所以_by列都显示用户名而不是ID.

but I don't know how to write it so both _by columns show usernames rather than IDs.

推荐答案

SELECT 
     complaint.complaint_text, 
     A.username, 
     B.username
FROM 
     complaint 
     LEFT JOIN user A ON A.user_id=complaint.opened_by 
     LEFT JOIN user B ON B.user_id=complaint.closed_by

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