INNER JOIN 同一个表
我正在尝试从同一个表中获取一些行.这是一个用户表:用户有 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.我已经编写了这样的代码:
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]
但它没有显示结果.我想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
条件上.
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]
编辑:如果用户没有父母,您可能应该使用 LEFT JOIN
.
Edit:
You should probably use LEFT JOIN
if there are users with no parents.
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