從平面數據集中的父子表中檢索數據

Question

由於現有的數據庫模式設計不正確，我必須以特殊方式編寫select語句，如this thread中所示。

SELECT MAX(CASE WHEN Name = 'C' THEN RelativePath END) AS C, 
    MAX(CASE WHEN Name = 'CC' THEN RelativePath END) AS CC, 
    MAX(CASE WHEN Name = 'S' THEN RelativePath END) AS S, 
    MAX(CASE WHEN Name = 'SC' THEN RelativePath END) AS SC, 
    MAX(CASE WHEN Name = 'R' THEN RelativePath END) AS R, 
    MAX(CASE WHEN Name = 'RC' THEN RelativePath END) AS RC 
FROM myTable 
WHERE ID = pId; 

現在，我需要將其輸出與其父表的select語句連接起來。親子表的結構如下：

Parent 
------------------- 
id -> the primary key 
third_party_id 
createdBy 
createdDate 
... 

Child 
------------------- 
id -> the primary key of its Parent table 
Name 
... 

select語句的我想要的輸出結果是一樣的東西對於一個給定的ID如下：

third_party_id, createdBy, createdDate, C, CC, S, SC, R, RC 

子表可能沒有給定父表鍵的條目。我使用左連接選擇語句，但無法獲得所需的結果。數據庫是mySQL。

如果單個select語句不起作用，如何爲輸出構造一個存儲過程？

Answer 1

SELECT 
    Parent.third_party_id, 
    Parent.createdBy, 
    Parent.createdDate, 
    Child.C, 
    Child.CC, 
    Child.S, 
    Child.SC, 
    Child.R, 
    Child.RC 
FROM 
    Parent 
LEFT OUTER JOIN 
(
    SELECT 
    ID, 
    MAX(CASE WHEN Name = 'C' THEN RelativePath END) AS C, 
    MAX(CASE WHEN Name = 'CC' THEN RelativePath END) AS CC, 
    MAX(CASE WHEN Name = 'S' THEN RelativePath END) AS S, 
    MAX(CASE WHEN Name = 'SC' THEN RelativePath END) AS SC, 
    MAX(CASE WHEN Name = 'R' THEN RelativePath END) AS R, 
    MAX(CASE WHEN Name = 'RC' THEN RelativePath END) AS RC 
    FROM myTable 
    GROUP BY ID 
) Child ON 
    Child.ID = Parent.ID 
WHERE 
    Parent.ID = pId;