MySQL數據透視表列數據作爲行

Question

我正在努力尋找解決這個MySQL問題的方法。我似乎無法理解如何去做。我有以下表格。

Question table 
+----+-------------+ 
| id | question | 
+----+-------------+ 
| 1 | Is it this? | 
| 2 | Or this? | 
| 3 | Or that? | 
+----+-------------+ 

Results Table 
+----+---------+--------+ 
| id | user_id | job_id | 
+----+---------+--------+ 
| 1 | 1  | 1  | 
| 2 | 1  | 3  | 
| 3 | 2  | 3  | 
+----+---------+--------+ 

Answers table 
+----+-------------------------+--------------+ 
| id | answer | fk_question_id | fk_result_id | 
+----+-------------------------+--------------+ 
| 1 | Yes | 1    | 1   | 
| 2 | No  | 2    | 1   | 
| 3 | Maybe | 3    | 1   | 
| 4 | Maybe | 1    | 2   | 
| 5 | No  | 2    | 2   | 
| 6 | Maybe | 3    | 2   | 
| 7 | Yes | 1    | 3   | 
| 8 | Yes | 2    | 3   | 
| 9 | No  | 3    | 3   | 
+----+-------------------------+--------------+ 

如果可能，我想顯示問題的答案作爲每個結果集的列，就像這樣。

+-----------+---------+--------+-------------+----------+----------+ 
| result_id | user_id | job_id | Is it this? | Or this? | Or that? | 
+-----------+---------+--------+-------------+----------+----------+ 
| 1   | 1  | 1  | Yes   | No  | Maybe | 
| 2   | 1  | 3  | Maybe  | No  | Maybe | 
| 3   | 2  | 3  | Yes   | Yes  | No  | 
+-----------+---------+--------+-------------+----------+----------+ 

任何幫助將不勝感激。

感謝

Answer 1

SELECT a.ID, 
     a.user_ID, 
     a.job_id, 
     MAX(CASE WHEN c.question = 'Is it this?' THEN b.answer END) 'Is it this?', 
     MAX(CASE WHEN c.question = 'Or this?' THEN b.answer END) 'Or this?', 
     MAX(CASE WHEN c.question = 'Or that? ' THEN b.answer END) 'Or that? ' 
FROM Results a 
     INNER JOIN Answers b 
      ON a.id = b.fk_result_id 
     INNER JOIN Question c 
      ON b.fk_question_id = c.ID 
GROUP BY a.ID, 
     a.user_ID, 
     a.job_id 

• SQLFiddle Demo

如果你有問題不明數量（特別是像1000米哈伊·馬太說：），動態版本很多必需的。

SET @sql = NULL; 
SELECT 
    GROUP_CONCAT(DISTINCT 
    CONCAT(
     'MAX(CASE WHEN c.question = ''', 
     question, 
     ''' then b.answer end) AS ', 
     CONCAT('`',question,'`') 
    ) 
) INTO @sql 
FROM Question; 

SET @sql = CONCAT('SELECT a.ID, 
          a.user_ID, 
          a.job_id, ', @sql, ' 
        FROM Results a 
          INNER JOIN Answers b 
           ON a.id = b.fk_result_id 
          INNER JOIN Question c 
           ON b.fk_question_id = c.ID 
        GROUP BY a.ID, 
          a.user_ID, 
          a.job_id'); 

PREPARE stmt FROM @sql; 
EXECUTE stmt; 
DEALLOCATE PREPARE stmt; 

• SQLFiddle Demo

輸出

╔════╦═════════╦════════╦═════════════╦══════════╦══════════╗ 
║ ID ║ USER_ID ║ JOB_ID ║ IS IT THIS? ║ OR THIS? ║ OR THAT? ║ 
╠════╬═════════╬════════╬═════════════╬══════════╬══════════╣ 
║ 1 ║  1 ║  1 ║ Yes   ║ No  ║ Maybe ║ 
║ 2 ║  1 ║  3 ║ Maybe  ║ No  ║ Maybe ║ 
║ 3 ║  2 ║  3 ║ Yes   ║ Yes  ║ No  ║ 
╚════╩═════════╩════════╩═════════════╩══════════╩══════════╝