#1193 - 未知系统变量 'id'

Question

花了8个小时检查这个问题，但没有任何结果，有人能说什么错了吗？

>SELECT id FROM posts AS post_id;SET categories.id  AS category_id;  
>SELECT title, contents, date_posted, categories, name FROM posts INNER JOIN 
>categories ON categories, id = posts, cat_id ORDER BY id DESC  

并得到一个错误 $ #1193 - 未知系统变量 'id'

我也尝试过这样的事情：

>SELECT id FROM posts AS post_id;  
>SELECT id FROM categories AS category_id;  
>SELECT COALESCE (title, contents, date_posted, categories, name) 
>FROM posts INNER JOIN categories ON categories, id = posts, cat_id
>ORDER BY id DESC

还有很多其他无法正常工作的员工。

工作查询：

 >SELECT posts . p_id AS post_id, categories . c_id AS category_id,  
    >title, contents, date_posted, categories . name   
    >FROM posts  
    >INNER JOIN categories ON categories . c_id = posts . cat_id  
    >ORDER BY posts.p_id DESC;  

Answer 1

尝试将数据库中的变量名称 id 更改为其他名称。 id 是保留名称。

Answer 2

如果我理解您的查询，请按以下方式使用-

SELECT pst.id AS post_id,cat.id AS category_id, title, contents, date_posted, categories, NAME 
FROM posts AS pst 
INNER JOIN categories cat ON cat.id = pst.cat_id 
ORDER BY pst.id DESC;

注意：您可以根据 cat.id 进行排序，然后进行相应更改。