【发布时间】：2020-10-14 08:25:39
【问题描述】：
我有一个 GROUP_CONCAT 选择的问题，它也应该包含类似于这个问题GROUP_CONCAT numbering 的行编号 不同之处在于我必须按多列分组。
例如，我有 2 个表 review 和 review_detail。
Schema (MySQL v5.5)
create table review (
`id` int(11) NOT NULL AUTO_INCREMENT,
`submission_id` int(11) NOT NULL,
PRIMARY KEY (`id`)
);
create table review_detail (
`id` int(11) NOT NULL AUTO_INCREMENT,
`review_id` int(11),
`category_id` int(11),
`rating` varchar(100),
PRIMARY KEY (`id`)
);
insert into review (`id`, `submission_id`) values (1, 1), (2, 1), (3, 2), (4, 3), (5,1), (6,3), (7,2), (8,3);
insert into review_detail (`review_id`, `category_id`, `rating`)
values
(1, 1, ' submission 1.1 cat 1'), (1, 2, ' submission 1.1 cat 2'),
(2, 1, ' submission 1.2 cat 1'), (2, 2, ' submission 1.2 cat 2'),
(3, 1, ' submission 2.1 cat 1'), (3, 2, ' submission 2.1 cat 2'),
(4, 1, ' submission 3.1 cat 1'), (4, 2, ' submission 3.1 cat 1'),
(5, 1, ' submission 1.3 cat 1'), (5, 2, ' submission 1.3 cat 2'),
(6, 1, ' submission 3.2 cat 1'), (6, 2, ' submission 3.2 cat 2'),
(7, 1, ' submission 2.2 cat 1'), (7, 2, ' submission 2.2 cat 2'),
(8, 1, ' submission 3.3 cat 1'), (6, 2, ' submission 3.3 cat 2')
;
查询 #1
SELECT * FROM review;
| id | submission_id |
| --- | ------------- |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 3 |
| 5 | 1 |
| 6 | 3 |
| 7 | 2 |
| 8 | 3 |
查询 #2
SELECT * FROM review_detail;
| id | review_id | category_id | rating |
| --- | --------- | ----------- | --------------------- |
| 1 | 1 | 1 | submission 1.1 cat 1 |
| 2 | 1 | 2 | submission 1.1 cat 2 |
| 3 | 2 | 1 | submission 1.2 cat 1 |
| 4 | 2 | 2 | submission 1.2 cat 2 |
| 5 | 3 | 1 | submission 2.1 cat 1 |
| 6 | 3 | 2 | submission 2.1 cat 2 |
| 7 | 4 | 1 | submission 3.1 cat 1 |
| 8 | 4 | 2 | submission 3.1 cat 1 |
| 9 | 5 | 1 | submission 1.3 cat 1 |
| 10 | 5 | 2 | submission 1.3 cat 2 |
| 11 | 6 | 1 | submission 3.2 cat 1 |
| 12 | 6 | 2 | submission 3.2 cat 2 |
| 13 | 7 | 1 | submission 2.2 cat 1 |
| 14 | 7 | 2 | submission 2.2 cat 2 |
| 15 | 8 | 1 | submission 3.3 cat 1 |
| 16 | 6 | 2 | submission 3.3 cat 2 |
提交的每条评论（外键 = submission_id）都有多个带有 category_id 的 review_detail 条目（在我的示例中，只有 2 个类别 (1,2) 与查询无关）。
我必须创建一个选择，让 GROUP_CONCAT 按submission_id 和category_id 分组。
Concat 字符串应返回Reviewer 1: {rating}, Reviewer 2: {rating}, Reviewer 3: {rating} etc.。
例如对于 submit_id = 1 和 category_id = 1 组 concat 应返回Reviewer 1: submission 1.1 cat 1, Reviewer 2: submission 1.2 cat 1, Reviewer 3: submission 1.3 cat 1。
但我无法正确获取组 concat 中的编号。
到目前为止，我已经进行了多次测试。
只有一个列计数器的组（有效）：
https://www.db-fiddle.com/f/6hA4Vft1mQGdw2Pew2An2T/3Reviewer 1: submission 1.1 cat 1 of review 1 / Reviewer 2: submission 3.3 cat 1 of review 8 / Reviewer 3: submission 2.2 cat 1 of review 7 / Reviewer 4: submission 3.2 cat 1 of review 6 / ... etc.
SELECT
--review.submission_id,
review_detail.category_id,
@i,
GROUP_CONCAT(
CONCAT(
'Reviewer ',
@i := @i + 1,
': ',
rating,
' of review ', review_id
)
SEPARATOR ' / '
) concatText,
@i := 0
FROM
review_detail
LEFT JOIN review ON review.id = review_detail.review_id,
(
SELECT
@i := 0
) init
GROUP BY
review_detail.category_id
ORDER BY
review_detail.category_id ASC
;
使用 if 进行测试并与 2 个分组列的字符串进行比较（不起作用）：
https://www.db-fiddle.com/f/3woAVSw5hrav15jAmuWVdT/3Reviewer 1: submission 1.1 cat 1 of review 1 / Reviewer 1: submission 1.2 cat 1 of review 2 / Reviewer 1: submission 1.3 cat 1 of review 5
SELECT
submission_id,
category_id,
@i,
@grp,
CONCAT_WS("-", submission_id, category_id) AS catgroup,
GROUP_CONCAT(
CONCAT(
'Reviewer ',
@i := IF(
@grp = CONCAT_WS("-", submission_id, category_id),
@i + 1,
IF(
@grp := CONCAT_WS("-", submission_id, category_id),
1,
1
)
),
': ',
rating,
' of review ', review_id
)
ORDER BY review_id, submission_id, category_id
SEPARATOR ' / '
) concatText
FROM
review_detail
LEFT JOIN review ON review.id = review_detail.review_id,
(
SELECT
@i := 0,
@grp := ''
) init
GROUP BY
review.submission_id,
review_detail.category_id
那么当多列分组时，有没有人知道如何在 GROUP_CONCAT 调用中正确编号？
【问题讨论】：
-
升级到 8.0 或 MariaDB 10.2 这样你就可以得到
ROW_NUMBER()。 -
感谢大家的解决方案。下面提到的每个解决方案都有效，因此我很难将赏金提供给特定的解决方案。如果我选择其他解决方案，我希望它不会惹恼您。我非常感谢下面的所有解决方案。
标签： mysql group-concat