MySQL连接返回空字段

我试图运行下面的脚本，但总是得到名称字段的空值

SELECT u.name AS _user_name, s.name AS _school_name
FROM fwg_files AS f
LEFT JOIN users AS u ON u.id = f.user_id
LEFT JOIN user_profiles AS up ON up.user_id = u.id
LEFT JOIN school AS s ON s.id = up.profile_value

在学校表上的JOIN中，我似乎遇到了问题，我试图选择s.id，但它也返回空值

表fwg_文件

id  | user_id
240 | 414
241 | 436

表用户

id  | name
414 | Name 1
436 | Name 2

表用户配置文件

user_id | profile_value
414     | "6"
436     | "14"

桌上学校

id | name

 6 | School 1
14 | School 2

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谢谢

不确定您的数据和架构，但是如果up.profile\u值类似于“123”，您可以尝试以下方法：

SELECT u.name AS _user_name, s.name AS _school_name
FROM fwg_files AS f
LEFT JOIN users AS u ON u.id = f.user_id
LEFT JOIN user_profiles AS up ON up.user_id = u.id
LEFT JOIN school AS s ON CONCAT('"', s.id, '"') = up.profile_value

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请从users和userprofiles表中分别显示一条记录