没有条件的 Group Concat

Question

我正在尝试重写我的查询以使用列而不是行。我有这个查询：

mysql> SELECT r.id as responseId, a.id as answerId, o.id, optionId, q.label as questionLabel, o.label as optionLabel
    -> FROM answer a
    -> INNER JOIN question q ON questionId = q.id
    -> INNER JOIN answer_options_option ao ON a.id = ao.answerId
    -> INNER JOIN `option` o ON ao.optionId = o.id
    -> INNER JOIN response r ON a.responseId = r.id
    -> ORDER BY r.id, a.id, o.id;

这给了我这个输出：

+------------+----------+----+----------+---------------+-------------+
| responseId | answerId | id | optionId | questionLabel | optionLabel |
+------------+----------+----+----------+---------------+-------------+
|          1 |        1 |  2 |        2 | Q1            | no          |
|          1 |        2 |  4 |        4 | Q2            | b           |
|          2 |        3 |  1 |        1 | Q1            | yes         |
|          2 |        4 |  3 |        3 | Q2            | a           |
|          2 |        4 |  4 |        4 | Q2            | b           |
|          2 |        4 |  5 |        5 | Q2            | c           |
+------------+----------+----+----------+---------------+-------------+

但我想得到这个输出：

+------------+-----------+-------+
| responseId | Q1        | Q2    |
+------------+-----------+-------+
|          1 | no        | b     |
|          2 | yes       | a,b,c |
+------------+-----------+-------+

所以我拼凑了这个查询：

mysql> SELECT r.id as responseId,
    -> IF(q.label = 'Q1', GROUP_CONCAT(o.label), NULL) as Q1,
    -> IF(q.label = 'Q2', GROUP_CONCAT(o.label), NULL) as Q2
    -> FROM answer a
    -> INNER JOIN question q ON questionId = q.id
    -> INNER JOIN answer_options_option ao ON a.id = ao.answerId
    -> INNER JOIN `option` o ON ao.optionId = o.id
    -> INNER JOIN response r ON a.responseId = r.id
    -> GROUP BY r.id;

但它给了我这个输出：

+------------+-----------+------+
| responseId | Q1        | Q2   |
+------------+-----------+------+
|          1 | no,b      | NULL |
|          2 | yes,a,b,c | NULL |
+------------+-----------+------+

甚至可以这样使用 GROUP_CONCAT 吗？还有其他方法可以完成我想做的事情吗？

这里是 Fiddle。

Answer 1

您需要将 GROUP_CONCAT 移到条件之外，以便您根据问题聚合选项，而不是仅仅根据问题获得整个聚合结果值：

SELECT r.id as responseId,
GROUP_CONCAT(CASE WHEN q.label = 'Q1' THEN o.label END ORDER BY o.label) as Q1, 
GROUP_CONCAT(CASE WHEN q.label = 'Q2' THEN o.label END ORDER BY o.label) as Q2
FROM answer a
INNER JOIN question q ON questionId = q.id
INNER JOIN answer_options_option ao ON a.id = ao.answerId
INNER JOIN `option` o ON ao.optionId = o.id
INNER JOIN response r ON a.responseId = r.id
GROUP BY r.id;

输出：

responseId  Q1      Q2
1           no      b
2           yes     a,b,c

Demo on dbfiddle

没有条件的 Group Concat

Group Concat without conditionals

mysql

group-concat