INNER JOIN同桌 [英] INNER JOIN same table
本文介绍了INNER JOIN同桌的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我正在尝试从同一张表中获取一些行.这是一个用户表:用户具有user_id
和user_parent_id
.
I am trying to get some rows from the same table. It's a user table: user has user_id
and user_parent_id
.
我需要获取user_id
行和user_parent_id
行.我已经编写了如下代码:
I need to get the user_id
row and user_parent_id
row. I have coded something like this:
SELECT user.user_fname, user.user_lname
FROM users as user
INNER JOIN users AS parent
ON parent.user_parent_id = user.user_id
WHERE user.user_id = $_GET[id]
但是它没有显示结果.我要显示用户记录及其父记录.
But it doesn't show the results. I want to display user record and its parent record.
推荐答案
我认为问题出在您的JOIN
状态.
I think the problem is in your JOIN
condition.
SELECT user.user_fname,
user.user_lname,
parent.user_fname,
parent.user_lname
FROM users AS user
JOIN users AS parent
ON parent.user_id = user.user_parent_id
WHERE user.user_id = $_GET[id]
修改:
如果有没有父母的用户,您应该使用LEFT JOIN
.
Edit:
You should probably use LEFT JOIN
if there are users with no parents.
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