为什么这个sql查询一直给我显示一个语法错误

Question

语法错误在下面的代码中显示为“as t3”。 我试图完全外部连接2表，但由于MySQL没有完全连接，即时通讯使用联合工会2左/右连接表。 对我来说，我无法找到任何语法错误什么那么，但它只是不会工作...

SELECT 
    name, f.author_nameauthor_id, c1, c2 
FROM 
(
    SELECT 
      author_id, c1, c2 
    FROM 
    (
     (SELECT 
       author_id, amount AS c1 
     FROM Author_Keyword_Count 
     WHERE keyword_id=19478) AS t1 

     LEFT OUTER JOIN 

     (SELECT 
       author_id, amount AS c2 
     FROM Author_Keyword_Count 
     WHERE keyword_id=33944) AS t2 

     ON author_id=author_id 
    ) 
    UNION 
    (
     (SELECT author_id, amount AS c1 FROM Author_Keyword_Count WHERE keyword_id=19478) AS t3 
     RIGHT OUTER JOIN 
     (SELECT author_id, amount AS c2 FROM Author_Keyword_Count WHERE keyword_id=33944) AS t4 
     ON author_id=author_id 
    ) 
) AS f 

LEFT OUTER JOIN Author ON author_id=id; 

Answer 1

一些观察包含下面...

SELECT name 
    , f.author_nameauthor_id 
    , c1 
    , c2 
    FROM 
    (SELECT author_id 
      , c1 
      , c2 
     FROM 
      ( !-- <-- something missing here!?! 
        (SELECT author_id 
         , amount c1 
         FROM Author_Keyword_Count 
        WHERE keyword_id = 19478 
       ) t1 
       LEFT 
       JOIN 
        (SELECT author_id 
         , amount c2 
         FROM Author_Keyword_Count 
        WHERE keyword_id = 33944 
       ) t2 
       ON author_id = author_id !-- <-- which author id equals which other author id!?!? 
      ) 
     UNION 
      ( !-- <-- something missing here!?!? 
       (SELECT author_id 
         , amount c1 
        FROM Author_Keyword_Count 
        WHERE keyword_id = 19478 
       ) t3 
      RIGHT 
      JOIN !-- for ease of conceptualising, consider restructuring your logic to use a LEFT JOIN instead of a RIGHT JOIN 
       (SELECT author_id 
         , amount c2 
        FROM Author_Keyword_Count 
        WHERE keyword_id = 33944 
       ) t4 
       ON author_id = author_id !-- <-- which author id equals which other author id!?!? 
      ) 
    ) f 
    LEFT 
    JOIN Author 
    ON author_id = id; !-- <-- which author id equals which id!?!? 

Conceptally，你写(SELECT 'x') a JOIN (SELECT 'y') b这是（我认为）无效。你可以写SELECT * FROM (SELECT 'x') a JOIN (SELECT 'y') b，但也许有一个更优雅的方式来构建这个查询 - 只要我们知道你实际上想要做什么。