[英]Find Students who have registered in selected subject by Dropdown in php
[英]I want to list the students who are not registered in the class
一个学生可以注册多个 class。 我想列出没有在 class 中注册的学生。 但是我找不到哪里出错了。
这是我的代码,列出了 class 中的内容:
SELECT users.id as id, users.rank, users.name_surname, users.status
FROM userClasses,users
WHERE userClasses.user = users.id
AND userClasses.classes = 2
这是我的代码,列出了那些未在 class 注册的代码:
SELECT users.id as id, users.rank, users.name_surname, users.status
FROM userClasses,users
WHERE userClasses.user = users.id
AND userClasses.classes <> 2
你能帮忙吗?
我也试过这段代码,它没有给出正确的结果。
SELECT users.* FROM
( SELECT users.*, userClasses.classes
FROM users
LEFT JOIN userClasses
ON users.id = userClasses.user
WHERE ((userClasses.classes <> 2)
OR (userClasses.classes IS NULL)) AND users.`rank`=1 )
users
LEFT JOIN classes
ON users.classes = classes.id;
SELECT users.id as id, users.rank, users.name_surname, users.status
FROM userClasses
INNER JOIN users ON userClasses.user = id
WHERE userClasses.classes <> '2'
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