仅在Join上解析左侧

Question

在下面的代码中，我想将表c_files cf与两个括号内的第二个查询的结果（别名x）结合起来。

SELECT f_cl_path f,cf.f_id, 'xx' as jo 
FROM c_files cf 
LEFT JOIN 
    (SELECT f_cl_path f, f_id, f_workgroup, 'yy' as jo FROM myOtherTable 
     WHERE f_workgroup ='1234' AND f_status<=2) x 
ON x.f_id=cf.f_id  
WHERE cf.f_workgroup='798190' and jo='xx';

我想只获得jo='xx'的元素。但这不起作用。当我使用jo='yy'尝试时，我会得到一个结果，但我需要jo='xx'。

Answer 1

看到您的评论后，也许这张图片可能会有所帮助。

如果我没错，你的情况会是这样的：

SELECT f_cl_path f,cf.f_id
FROM c_files cf
LEFT JOIN (SELECT f_cl_path f, f_id, f_workgroup FROM myOtherTable 
     WHERE f_workgroup ='1234' AND f_status<=2) as x
ON x.f_id=cf.f_id  
WHERE cf.f_workgroup='798190' and x.f_id IS NULL