的Sql子查詢不工作 「ORA-00904： 」A2 ID_USER「。」 「：無效的標識符」

Question

我試圖在甲骨文

SELECT A1.ID_USER,A1.CNAME, 
(SELECT CNAME 
    FROM 
    (SELECT CNAME,COUNTER 
    FROM 
     (SELECT id_Category AS IDCATEGORT,COUNT(*) AS COUNTER 
     FROM gamescateg 
     WHERE id_game IN 
     (SELECT ID_GAME 
     FROM UserGames 
     WHERE id_user=UsersGamers.ID_USER 
     ) 
     GROUP BY id_Category 
     ) 
    JOIN Categories 
    ON id_Category =IDCATEGORT 
    ORDER BY COUNTER DESC 
    ) 
    WHERE rownum = 1 
) AS FAVORITECATEGORY 
FROM UsersGamers A1 
JOIN UsersGamers A2 ON A1.ID_USER= A2.ID_USER 

運行此查詢，但我得到的錯誤

ORA-00904: "A2"."ID_USER": invalid identifier 

A2.ID_USER需要做子查詢 爲什麼？ 如何解決？ 你能幫助我嗎？

我解決它BY CREATE FUNCTION

CREATE OR REPLACE FUNCTION FAVORITECATEGORYfunc(idnumber NUMBER) 
    RETURN VARCHAR2 
IS 
    l_conc_names VARCHAR2(32676); 
BEGIN 
    SELECT CNAME INTO l_conc_names 
    FROM 
    (SELECT CNAME,COUNTER 
    FROM 
     (SELECT id_Category AS IDCATEGORT,COUNT(*) AS COUNTER 
     FROM gamescateg 
     WHERE id_game IN 
     (SELECT ID_GAME 
     FROM UserGames 
     WHERE id_user=idnumber 
     ) 
     GROUP BY id_Category 
     ) 
    JOIN Categories 
    ON id_Category =IDCATEGORT 
    ORDER BY COUNTER DESC 
    ) 
    WHERE rownum = 1; 
    RETURN l_conc_names; 
END; 

和查詢是

select CNAME,FAVORITECATEGORYfunc(id_user) from usersgamers 

感謝幫助:)

Answer 1

我已經擴大您的查詢，使其更具可讀性並評論了問題（無效標識符）。有一個引用A2不能成爲A2的別名。

select A1.ID_USER, A1.CNAME, 
(
    SELECT CNAME FROM 
    (
     SELECT CNAME, COUNTER 
     FROM 
     (
      SELECT id_Category AS IDCATEGORT, 
      COUNT(*) AS COUNTER 
      FROM gamescateg 
      WHERE id_game IN 
      (
       SELECT ID_GAME FROM UserGames 
       WHERE id_user=A2.ID_USER /* your problem is here */ 
      ) 
      GROUP BY id_Category 
     ) 
     JOIN Categories 
     ON id_Category =IDCATEGORT 
     ORDER BY COUNTER DESC 
    ) 
    WHERE rownum = 1 
) AS FAVORITECATEGORY 
FROM UsersGamers A1 
JOIN UsersGamers A2 
ON A1.ID_USER= A2.ID_USER 

你有沒有考慮重寫這個以避免這麼多的嵌套查詢？而不是將它們一個包裝到另一箇中，而是嘗試使用連接對最喜歡的類別進行構造。

Answer 2

試着像這樣寫，並確保你得到了期望的結果。

SELECT A1.ID_USER, 
     A1.CNAME, 
     (SELECT CNAME 
      FROM 
      (SELECT CNAME, 
        COUNTER 
       FROM 
       (SELECT id_Category AS IDCATEGORT, 
         COUNT(*) AS COUNTER 
       FROM gamescateg 
       WHERE id_game IN 
        (SELECT ID_GAME 
         FROM UserGames 
         WHERE id_user=UsersGamers.ID_USER --replaced A2 with UsersGamers 
        ) 
       GROUP BY id_Category 
       ) 
       JOIN Categories ON id_Category =IDCATEGORT 
       ORDER BY COUNTER DESC 
      ) 
      WHERE rownum = 1 
     ) AS FAVORITECATEGORY 
FROM UsersGamers A1 
JOIN UsersGamers A2 ON A1.ID_USER= A2.ID_USER 

Answer 3

實質上，膚淺的修復不會修復查詢。所以，請解釋你正在嘗試做什麼。我懷疑查詢比需要的複雜得多。而且，這很難破譯。

從表面上看，您的問題是您使用的是表名而不是別名。所以，有人會認爲寫這樣的查詢將解決問題：

SELECT A1.ID_USER, A1.CNAME, 
     (SELECT CNAME 
     FROM (SELECT CNAME, COUNTER 
       FROM (SELECT id_Category AS IDCATEGORT, COUNT(*) AS COUNTER 
        FROM gamescateg 
        WHERE id_game IN (SELECT ug.ID_GAME 
             FROM UserGames ug 
             WHERE ug.id_user = UsersGamers.ID_USER 
            ) 
        GROUP BY id_Category 
       ) cc JOIN 
        Categories c 
        ON c.id_Category = cc.IDCATEGORT 
      ORDER BY COUNTER DESC 
      ) 
     WHERE rownum = 1 
     ) AS FAVORITECATEGORY 
FROM UsersGamers A1 JOIN 
    UsersGamers A2 
    ON A1.ID_USER = A2.ID_USER; 

但是，唉，它不會。 Oracle限制相關子查詢的範圍深度。所以，這不能解決問題;你會得到另一個錯誤。

這樣的查詢可能會做的最合理的事情是獲取給定用戶最常見的類別。如果是這樣的話：

SELECT u.* 
FROM (SELECT ugr.ID_USER, ugr.CNAME, c.cname, COUNT(*) as cnt, 
      ROW_NUMBER() OVER (PARTITION BY ugr.ID_USER, ugr.CNAME 
           ORDER BY COUNT(*) DESC 
           ) as seqnum 
     FROM UsersGamers ugr JOIN 
      UserGames ug 
      ON ugr.ID_USER = ug.ID_USER JOIN 
      Categories c 
      ON c.id_Category = ug.id_Category 
     GROUP BY ugr.ID_USER, ugr.CNAME 
    ) u 
WHERE seqnum = 1;