修改SELECT查詢以創建堆積條形圖

Question

我有一個針對展示位置應用跟蹤系統的查詢，該系統顯示每個學習計劃放置和取消放置的學生人數。儘管查詢返回了期望的結果，但我努力的創建了一個APEX堆棧條形圖。

查詢：

SELECT programme_name, 
      SUM(CASE WHEN (cv_approval_date IS NOT NULL AND application_status_id <> 7) OR 
         application_status_id IS NULL 
        THEN 1 ELSE 0 END) as Unplaced, 
      SUM(CASE WHEN (cv_approval_date IS NOT NULL AND application_status_id <> 7) OR 
         application_status_id IS NULL 
        THEN 0 ELSE 1 END) as Placed 
    FROM programme LEFT JOIN 
     student USING (programme_id) LEFT JOIN 
     application USING (student_id) 
    GROUP BY programme_name; 

輸出：

PROGRAMME_NAME        | PLACED | UNPLACED 
    BSc (Hons) Computer Science     | 2  | 2 
    BSc (Hons) Computing and Games Development | 1  | 0 
    BSc (Hons) Web Applications Development  | 0  | 1 
    BSc (Hons) Marine Biology and Coastal Ecology | 1  | 0 

該圖被認爲類似於此 - x軸被計劃，Y軸被學生的數量放置，和未放置的：

http://ruepprich.files.wordpress.com/2011/03/stacked_bar.png?w=550&h=386

我該如何去做這件事？任何幫助將不勝感激！

Answer 1

在Apex中創建圖表時，您可以單擊「圖表查詢示例」查看某些適用於該圖表類型的示例查詢。

在堆積條形圖的情況下，下面的例子給出：

SELECT NULL LINK, 
     ENAME LABEL, 
     SAL "Salary", 
     COMM "Commission" 
FROM EMP 
ORDER BY ENAME 

在你的情況我想你會希望你的查詢提出以下格式：

SELECT NULL LINK, 
     programme_name AS LABEL, 
     SUM(...) AS "Unplaced", 
     SUM(...) AS "Placed" 
FROM ...