我很难找到解决这个MySQL问题的方法。我似乎无法理解如何做到这一点。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 |
+----+-------------------------+--------------+
如果可能的话,我想将问题答案显示为每个结果集的列,如下所示。
+-----------+---------+--------+-------------+----------+----------+
| 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 |
+-----------+---------+--------+-------------+----------+----------+
非常感谢任何帮助。
由于
答案 0 :(得分:3)
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
如果您有不知道的问题数量(特别是1000,如Matei Mihai所说),则需要动态版本。
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;
输出
╔════╦═════════╦════════╦═════════════╦══════════╦══════════╗
║ 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 ║
╚════╩═════════╩════════╩═════════════╩══════════╩══════════╝