Question

假设我有桌子＆＃39;组织＆＃39;有两列＆＃39;姓名＆＃39;和＆＃39;角色＆＃39;字段＆＃39;名称＆＃39;包含一个字符串，类似的＆＃39;角色＆＃39;可以是以下列表中的字符串：[＆＃39;管理员＆＃39;，＆＃39;主持人＆＃39;，＆＃39;用户＆＃39;]。

我想执行一个查询，向我打印按角色排序的用户。例如，有以下起始表：

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

我想获得以下查询：

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

我到目前为止提出的最佳解决方案如下，但我希望有一个更紧凑的解决方案。我需要的是分离列然后重新加入它们，但我不知道如何做到这一点......

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

要执行此操作，您可以使用等效的ROW_NUMBER和GROUP BY计算的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

的 SqlFiddleDemo

输出：

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

MySQL使用VARCHAR

1 个答案: