MySQL使用VARCHAR進行數據透視

Question

假設我的表'Organization'有兩列'Name'和'Role'。 字段'Name'包含一個字符串，類似'Role'可以是以下列表中的字符串：['Admin'，'Moderator'，'User']。

我想執行一個查詢，打印我按角色排序的用戶。 例如，有以下起始表：

+++++++++++++++++++++++
+   Name   +   Role   +
+++++++++++++++++++++++
+   Sara   +   User   +
+   Tony   +   Admin  +
+   John   +   User   +
+++++++++++++++++++++++

我想獲得以下查詢：

++++++++++++++++++++++++++++++++++++++++
+   Admin   +   Moderator   +   User   +
++++++++++++++++++++++++++++++++++++++++
+   Tony    +      NULL     +   Sara   +
+   NULL    +      NULL     +   John   +
++++++++++++++++++++++++++++++++++++++++

到目前為止我提出的最佳解決方案如下，但我希望有一個更緊湊的解決方案。 我需要的是分離列然后重新加入它們，但我不知道如何做到這一點......

SELECT CASE WHEN Role = 'Admin' THEN Name END AS 'Admin', 
CASE WHEN Role = 'Moderator' THEN Name END AS 'Moderator', 
CASE WHEN Role= 'User' THEN Name END AS 'User'
FROM Organization;

++++++++++++++++++++++++++++++++++++++++
+   Admin   +   Moderator   +   User   +
++++++++++++++++++++++++++++++++++++++++
+   NULL    +      NULL     +   Sara   +
+   Tony    +      NULL     +   NULL   +
+   NULL    +      NULL     +   John   +
++++++++++++++++++++++++++++++++++++++++

Answer 1

為此，您可以使用等效的ROW_NUMBER和GROUP BY計算的RowNumber列：

SELECT 
    MAX(CASE WHEN Role = 'Admin' THEN Name END) AS `Admin`, 
    MAX(CASE WHEN Role = 'Moderator' THEN Name END) AS `Moderator`, 
    MAX(CASE WHEN Role = 'User' THEN Name END) AS `User`
FROM (
      SELECT *
        ,@row_num := IF(@prev_value=concat_ws('',t.Role),@row_num+1,1) AS RowNumber
        ,@prev_value := concat_ws('',t.Role)  
      FROM Organization t,
         (SELECT @row_num := 1) x,
         (SELECT @prev_value := '') y
      ORDER BY t.Role   
     ) AS sub
GROUP BY RowNumber

SqlFiddleDemo

輸出：

╔═════════╦════════════╦══════╗
║ Admin   ║ Moderator  ║ User ║
╠═════════╬════════════╬══════╣
║ Tony    ║ (null)     ║ Sara ║
║ (null)  ║ (null)     ║ John ║
╚═════════╩════════════╩══════╝