單個字段的子查詢創建多個記錄

我的場景：請求可能有多個（最多3個）拒絕代碼。第一個是主要拒收代碼，第二個（第二個和第三個）拒收代碼是可選的。要確定拒絕代碼排名，有一個名爲reject_rowId的字段。如果reject_rowId ='1'，那麼這是主要拒絕。如果rejection_rowId ='2'，那麼這是第二次拒絕。如果它是'3'，那是第三。現在，我試圖在一條記錄中顯示屬於一個請求的所有reject_code值，而不是爲每個reject_code存儲一條記錄。我遇到了麻煩，並想知道是否有人可以解釋爲什麼我的SQL無法正常工作。單個字段的子查詢創建多個記錄

我的SQL看起來基本上是這樣的;

SELECT DISTINCT rea.id 
    ,(SELECT rejection_code 
     FROM rejection t1 
     INNER JOIN reason t2 ON t1.rowId = t2.rowId 
     WHERE t1.rejection_rowId = '1' 
     AND t1.rowId = REA.rowId) AS rejection1 

    ,(SELECT rejection_code 
     FROM rejection t1 
     INNER JOIN reason t2 ON t1.rowId = t2.rowId 
     WHERE t1.rejection_rowId = '2' 
     AND t1.rowId = REA.rowId) AS rejection2 

    ,(SELECT rejection_code 
     FROM rejection t1 
     INNER JOIN reason t2 ON t1.rowId = t2.rowId 
     WHERE t1.rejection_rowId = '3' 
     AND t1.rowId = REA.rowId) AS rejection3 

FROM reason rea 
INNER JOIN rejection rej ON rea.rowId = rej.rowId 
WHERE rea.id = '12345';

通過上面的SQL生成的輸出...

id | rejection1 | rejection2 | rejection3 
12345 | 26   | NULL  | NULL 
12345 | NULL  | 51   | NULL 
12345 | NULL  | NULL  | 3

我試圖（和失敗）生成的輸出爲...

id | rejection1 | rejection2 | rejection3 
12345 | 26   | 51   | 3

如果有人可以幫助我確定並解決問題，我將不勝感激。謝謝！

來源

2016-02-03 L. West

我認爲你正在嘗試做這樣的事情：

SELECT 
    rea.id, 
    MAX(CASE WHEN rej.rejection_rowId = '1' THEN rej.rejection_code END) AS rejection1, 
    MAX(CASE WHEN rej.rejection_rowId = '2' THEN rej.rejection_code END) AS rejection2, 
    MAX(CASE WHEN rej.rejection_rowId = '3' THEN rej.rejection_code END) AS rejection3, 
FROM 
    reason rea 
    INNER JOIN rejection rej ON rea.rowId = rej.rowId 
WHERE 
    rea.id = '12345' 
GROUP BY rea.id

沒有必要一次又一次同樣的表之間的加入，使用子查詢來實現你需要的是根本沒有必要的，成本很多。

使用GROUP BY子句，可以將結果限制爲一行。使用集合函數內的條件時，只有在實際存在某個列時纔會在列中顯示拒絕，並且您可以將它們拆分爲單獨的列。

來源

2016-02-03 18:10:46

真棒，謝謝！這個伎倆。我早些時候嘗試過使用case語句，但我沒有想到使用聚合函數和group by語句。 –

試試這個：

中的款項：

SELECT DISTINCT rea.id 
    ,SUM(SELECT rejection_code 
     FROM rejection t1 
     INNER JOIN reason t2 ON t1.rowId = t2.rowId 
     WHERE t1.rejection_rowId = '1' 
     AND t1.rowId = REA.rowId) AS rejection1 

    ,SUM(SELECT rejection_code 
     FROM rejection t1 
     INNER JOIN reason t2 ON t1.rowId = t2.rowId 
     WHERE t1.rejection_rowId = '2' 
     AND t1.rowId = REA.rowId) AS rejection2 

    ,SUM(SELECT rejection_code 
     FROM rejection t1 
     INNER JOIN reason t2 ON t1.rowId = t2.rowId 
     WHERE t1.rejection_rowId = '3' 
     AND t1.rowId = REA.rowId) AS rejection3 

FROM reason rea 
INNER JOIN rejection rej ON rea.rowId = rej.rowId 
WHERE rea.id = '12345' 
GROUP BY rea.id ;

馬克斯：

SELECT DISTINCT rea.id 
    ,MAX(SELECT rejection_code 
     FROM rejection t1 
     INNER JOIN reason t2 ON t1.rowId = t2.rowId 
     WHERE t1.rejection_rowId = '1' 
     AND t1.rowId = REA.rowId) AS rejection1 

    ,MAX(SELECT rejection_code 
     FROM rejection t1 
     INNER JOIN reason t2 ON t1.rowId = t2.rowId 
     WHERE t1.rejection_rowId = '2' 
     AND t1.rowId = REA.rowId) AS rejection2 

    ,MAX(SELECT rejection_code 
     FROM rejection t1 
     INNER JOIN reason t2 ON t1.rowId = t2.rowId 
     WHERE t1.rejection_rowId = '3' 
     AND t1.rowId = REA.rowId) AS rejection3 

FROM reason rea 
INNER JOIN rejection rej ON rea.rowId = rej.rowId 
WHERE rea.id = '12345' 
GROUP BY rea.id ;

來源

2016-02-03 18:10:56

單個字段的子查詢創建多個記錄

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