如何将行值连接到动态查询中的列名称

Question

我正在开发一个允许可配置问题和答案的应用程序.目前最多可以有20个答案,但可能更少.

我的结构如下:

问题

+----+--------+--------------+-------------+
| ID | FormId | QuestionText | AnswerField |
+----+--------+--------------+-------------+
|  1 |      1 | Name         | Answer01    |
|  2 |      1 | Address      | Answer02    |
|  3 |      1 | Phone        | Answer03    |
|  4 |      1 | Email        | Answer04    |
|  5 |      2 | First Name   | Answer01    |
|  6 |      2 | Surname      | Answer02    |
+----+--------+--------------+-------------+

答案

+----+--------+----------+------------+--------------+--------------+----------------+----------+----------+
| ID | FormId | RecordId |  Answer01  |   Answer02   |   Answer03   |    Answer04    | Answer05 | Answer06 |
+----+--------+----------+------------+--------------+--------------+----------------+----------+----------+
|  1 |      1 |        1 | Bob Smith  | Bobs Address | 01234 111222 | bob@smith.com  | Null     | Null     |
|  2 |      1 |        2 | Joe Bloggs | Joes Address | 04321 333444 | joe@bloggs.com | Null     | Null     |
|  3 |      2 |        3 | David      | Jones        | Null         | Null           | Null     |          |
+----+--------+----------+------------+--------------+--------------+----------------+----------+----------+

所以在Questions表中,AnswerField Answer01映射到Answers表中的Answer01列

我想做的是得到一个类似于的结果集:

表格ID 1和记录ID 1:

+--------------+---------------+
| QuestionText |    Answer     |
+--------------+---------------+
| Name         | Bob Smith     |
| Address      | Bobs Address  |
| Phone        | 01234 111222  |
| Email        | bob@smith.com |
+--------------+---------------+

然后对于表单ID 2和记录ID 3:

+--------------+---------+
| QuestionText | Answer  |
+--------------+---------+
| First Name   | David   |
| Surname      | Jones   |
+--------------+---------+

我尝试过使用数据透视表:

SELECT QuestionText, Answer01, Answer02, Answer03, Answer04
FROM (
    SELECT DISTINCT Q.AnswerField, Q.QuestionText, Q.ID, A.Answer01, A.Answer02, A.Answer03, A.Answer04
    FROM Questions Q
    INNER JOIN Answers A ON A.FormId= Q.FormId
    WHERE A.ID = 17
) 
AS src
PIVOT (MAX(question_id) FOR Answer IN(answer_01, answer_02, answer_03, answer_04)) AS pvt

但是这会重复所有列中的答案:

+--------------+-----------+--------------+--------------+---------------+
| QuestionText | Answer01  |   Answer02   |   Answer03   |   Answer04    |
+--------------+-----------+--------------+--------------+---------------+
| Name         | Bob smith | Bobs Address | 01234 111222 | bob@smith.com |
| Address      | Bob smith | Bobs Address | 01234 111222 | bob@smith.com |
| Phone        | Bob smith | Bobs Address | 01234 111222 | bob@smith.com |
| Email        | Bob smith | Bobs Address | 01234 111222 | bob@smith.com |
+--------------+-----------+--------------+--------------+---------------+

这显然是不对的.

任何人都可以建议如何在SQL Server存储过程中完成这项工作吗？

Answer 1

首先,你的Answers桌子设计非常好.该表未规范化,当您想要返回数据时会导致问题.如果可能,您需要重组该表.

如果您无法重新设计表格,则必须取消回答表格,以便能够轻松加入问题的答案.

UNPIVOT将获取您的列并将其转换为行.unpivot代码将是:

select formid, RecordId, answer, answercol
from answers a
unpivot
(
  answer
  for answerCol in ([Answer01], [Answer02], [Answer03], 
                    [Answer04], [Answer05], [Answer06])
) unpiv;

请参阅SQL Fiddle with Demo.这给出了一个结果:

| FORMID | RECORDID |         ANSWER | ANSWERCOL |
--------------------------------------------------
|      1 |        1 |      Bob Smith |  Answer01 |
|      1 |        1 |   Bobs Address |  Answer02 |
|      1 |        1 |   01234 111222 |  Answer03 |
|      1 |        1 |  bob@smith.com |  Answer04 |

一旦数据在行中,您就可以加入问题表以返回所需的结果:

select q.questiontext, d.answer
from questions q
inner join
(
  select formid, RecordId, answer, answercol
  from answers a
  unpivot
  (
    answer
    for answerCol in ([Answer01], [Answer02], [Answer03], 
                      [Answer04], [Answer05], [Answer06])
  ) unpiv
) d
  on q.AnswerField = d.answercol
  and q.formid = d.formid
where d.recordid = 1;

请参阅SQL Fiddle with Demo.这给出了一个结果:

| QUESTIONTEXT |        ANSWER |
--------------------------------
|         Name |     Bob Smith |
|      Address |  Bobs Address |
|        Phone |  01234 111222 |
|        Email | bob@smith.com |