GROUP_CONCAT 多列分组依据编号
GROUP_CONCAT numbering with multiple columns group by
我有一个 GROUP_CONCAT select 的问题，它也应该包含类似于这个问题的行编号
区别在于我必须按多列分组。
例如，我有 2 个表 review 和 review_detail。
架构（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 |
提交的每个评论（外键 = submission_id）都有多个 review_detail 条目 category_id（在我的示例中只有 2 个类别 (1,2) 不相关用于查询）。
我必须创建一个 select，其中我得到按 submission_id 和 category_id.
分组的 GROUP_CONCAT
Concat 字符串应该return
Reviewer 1: {rating}, Reviewer 2: {rating}, Reviewer 3: {rating} etc..
例如对于 submission_id = 1 和 category_id = 1，组连接应该 return
Reviewer 1: submission 1.1 cat 1, Reviewer 2: submission 1.2 cat 1, Reviewer 3: submission 1.3 cat 1.
但是我无法在组 concat 中正确编号。
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/3
Reviewer 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/3
Reviewer 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
那么有谁知道在多个列分组时正确获取 GROUP_CONCAT 调用中的编号的方法吗？
您应该避免在生产代码中使用 user-defined 变量。
在 manual for MySQL 5.6 中说：
As a general rule, other than in SET statements, you should never
assign a value to a user variable and read the value within the same
statement.
甚至在 documentation for 8.0 中也指出：
The order of evaluation for expressions involving user variables is
undefined. For example, there is no guarantee that SELECT @a, @a:=@a+1
evaluates @a first and then performs the assignment.
在未来的版本中，这可能不再完全有效：
Previous releases of MySQL made it possible to assign a value to a
user variable in statements other than SET. This functionality is
supported in MySQL 8.0 for backward compatibility but is subject to
removal in a future release of MySQL.
所以这是一个没有 user-defined 变量的解决方案：
SELECT
r.submission_id,
rd.category_id,
GROUP_CONCAT(CONCAT('Reviewer ', (SELECT COUNT(*) + 1
FROM review
JOIN review_detail ON review.id = review_detail.review_id
WHERE r.submission_id = review.submission_id
AND review_detail.category_id = rd.category_id
AND review_detail.id < rd.id
), ': ', rating, ' of review ', review_id) ORDER BY rating SEPARATOR ' / ') AS shorter_column_name
FROM
review r
JOIN review_detail rd ON rd.review_id = r.id
GROUP BY r.submission_id, rd.category_id;
哪个returns
+---------------+-------------+-----------------------------------------------------------------------------------------------------------------------------------------------+
| submission_id | category_id | shorter_column_name |
+---------------+-------------+-----------------------------------------------------------------------------------------------------------------------------------------------+
| 1 | 1 | Reviewer 1: submission 1.1 cat 1 of review 1 / Reviewer 2: submission 1.2 cat 1 of review 2 / Reviewer 3: submission 1.3 cat 1 of review 5 |
| 1 | 2 | Reviewer 1: submission 1.1 cat 2 of review 1 / Reviewer 2: submission 1.2 cat 2 of review 2 / Reviewer 3: submission 1.3 cat 2 of review 5 |
| 2 | 1 | Reviewer 1: submission 2.1 cat 1 of review 3 / Reviewer 2: submission 2.2 cat 1 of review 7 |
| 2 | 2 | Reviewer 1: submission 2.1 cat 2 of review 3 / Reviewer 2: submission 2.2 cat 2 of review 7 |
| 3 | 1 | Reviewer 1: submission 3.1 cat 1 of review 4 / Reviewer 2: submission 3.2 cat 1 of review 6 / Reviewer 3: submission 3.3 cat 1 of review 8 |
| 3 | 2 | Reviewer 1: submission 3.1 cat 1 of review 4 / Reviewer 2: submission 3.2 cat 2 of review 6 / Reviewer 3: submission 3.3 cat 2 of review 6 |
+---------------+-------------+-----------------------------------------------------------------------------------------------------------------------------------------------+
修复您的查询。
基本问题是表本质上是未排序的，这就是为什么 MySQL 优化器删除了 ORDER BY.
在MySQL中是否足以将所有表放在FROM子句中并使用顺序进行子查询，mysql将保留它。
在 Mariadb 中，这还不够您还添加了一个 LIMIT 18446744073709551615 以便优化器将保留它
架构（MySQL v5.5）
查询#1
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 := @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
(SELECT review_id, submission_id, category_id,`rating` FROM review_detail
LEFT JOIN review ON review.id = review_detail.review_id
ORDER BY review_id, submission_id, category_id ) t1,
(
SELECT
@i := 0,
@grp := ''
) init
GROUP BY
submission_id,
category_id;
结果
| submission_id | category_id | @i | @grp | catgroup | concatText |
| ------------- | ----------- | --- | ---- | -------- | --------------------------------------------------------------------------------------------------------------------------------------------- |
| 1 | 1 | 0 | | 1-1 | Reviewer 3: submission 1.1 cat 1 of review 1 / Reviewer 2: submission 1.2 cat 1 of review 2 / Reviewer 1: submission 1.3 cat 1 of review 5 |
| 1 | 2 | 3 | 1-1 | 1-2 | Reviewer 3: submission 1.1 cat 2 of review 1 / Reviewer 2: submission 1.2 cat 2 of review 2 / Reviewer 1: submission 1.3 cat 2 of review 5 |
| 2 | 1 | 3 | 1-2 | 2-1 | Reviewer 1: submission 2.1 cat 1 of review 3 / Reviewer 2: submission 2.2 cat 1 of review 7 |
| 2 | 2 | 2 | 2-1 | 2-2 | Reviewer 2: submission 2.1 cat 2 of review 3 / Reviewer 1: submission 2.2 cat 2 of review 7 |
| 3 | 1 | 2 | 2-2 | 3-1 | Reviewer 2: submission 3.1 cat 1 of review 4 / Reviewer 1: submission 3.2 cat 1 of review 6 / Reviewer 3: submission 3.3 cat 1 of review 8 |
| 3 | 2 | 3 | 3-1 | 3-2 | Reviewer 3: submission 3.1 cat 1 of review 4 / Reviewer 2: submission 3.3 cat 2 of review 6 / Reviewer 1: submission 3.2 cat 2 of review 6 |
您需要使用 tow-step 子查询按审稿人编号排序。
SET @i := 0;
SET @grp := '';
SELECT
submission_id,
category_id,
GROUP_CONCAT(
CONCAT(
'Reviewer ',
i,
': ',
rating,
' of review ', review_id
)
ORDER BY i
SEPARATOR ' / '
) concatText
FROM
-- second, add numbering
(
SELECT *,
@i := IF(
@grp = @grp := CONCAT_WS('-',submission_id,category_id),
@i + 1, 1) i
FROM
-- first, sort for numbering
(
SELECT
review_id,
submission_id,
category_id,
rating
FROM review_detail LEFT JOIN review ON review.id = review_detail.review_id
ORDER BY
submission_id,
category_id,
review_id
) t1
) t2
GROUP BY
submission_id,
category_id
;
为了完整起见，我还添加了如何在 Mysql 8.0
中完成的解决方案
它适用于 COUNT(*)
with base as (
SELECT
review_id,
submission_id,
category_id,
rating,
count(*) over (partition by submission_id,category_id order by review_id) num
FROM review_detail LEFT JOIN review ON review.id = review_detail.review_id
ORDER BY
submission_id,
category_id,
review_id
)
select
submission_id,
category_id,
group_concat(concat('Reviewer', num, ': ', rating, ' of review ', review_id ) separator ', ') concattext
from base
group by
submission_id,
category_id
;
或ROW_NUMBER()
with base as (
SELECT
review_id,
submission_id,
category_id,
rating,
ROW_NUMBER() over (partition by submission_id,category_id order by review_id) num
FROM review_detail
LEFT JOIN review ON review.id = review_detail.review_id
ORDER BY
submission_id,
category_id,
review_id
)
SELECT
submission_id,
category_id,
group_concat(concat('Reviewer', num, ': ', rating, ' of review ', review_id ) separator ', ') concattext
from base
group by
submission_id,
category_id
;
我有一个 GROUP_CONCAT select 的问题，它也应该包含类似于这个问题的行编号
例如，我有 2 个表 review 和 review_detail。
架构（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 |
提交的每个评论（外键 = submission_id）都有多个 review_detail 条目 category_id（在我的示例中只有 2 个类别 (1,2) 不相关用于查询）。
我必须创建一个 select，其中我得到按 submission_id 和 category_id.
Concat 字符串应该return
Reviewer 1: {rating}, Reviewer 2: {rating}, Reviewer 3: {rating} etc..
例如对于 submission_id = 1 和 category_id = 1，组连接应该 return
Reviewer 1: submission 1.1 cat 1, Reviewer 2: submission 1.2 cat 1, Reviewer 3: submission 1.3 cat 1.
但是我无法在组 concat 中正确编号。
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/3
Reviewer 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/3
Reviewer 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
那么有谁知道在多个列分组时正确获取 GROUP_CONCAT 调用中的编号的方法吗？
您应该避免在生产代码中使用 user-defined 变量。
在 manual for MySQL 5.6 中说：
As a general rule, other than in SET statements, you should never assign a value to a user variable and read the value within the same statement.
甚至在 documentation for 8.0 中也指出：
The order of evaluation for expressions involving user variables is undefined. For example, there is no guarantee that
SELECT @a, @a:=@a+1evaluates@afirst and then performs the assignment.
在未来的版本中，这可能不再完全有效：
Previous releases of MySQL made it possible to assign a value to a user variable in statements other than SET. This functionality is supported in MySQL 8.0 for backward compatibility but is subject to removal in a future release of MySQL.
所以这是一个没有 user-defined 变量的解决方案：
SELECT
r.submission_id,
rd.category_id,
GROUP_CONCAT(CONCAT('Reviewer ', (SELECT COUNT(*) + 1
FROM review
JOIN review_detail ON review.id = review_detail.review_id
WHERE r.submission_id = review.submission_id
AND review_detail.category_id = rd.category_id
AND review_detail.id < rd.id
), ': ', rating, ' of review ', review_id) ORDER BY rating SEPARATOR ' / ') AS shorter_column_name
FROM
review r
JOIN review_detail rd ON rd.review_id = r.id
GROUP BY r.submission_id, rd.category_id;
哪个returns
+---------------+-------------+-----------------------------------------------------------------------------------------------------------------------------------------------+
| submission_id | category_id | shorter_column_name |
+---------------+-------------+-----------------------------------------------------------------------------------------------------------------------------------------------+
| 1 | 1 | Reviewer 1: submission 1.1 cat 1 of review 1 / Reviewer 2: submission 1.2 cat 1 of review 2 / Reviewer 3: submission 1.3 cat 1 of review 5 |
| 1 | 2 | Reviewer 1: submission 1.1 cat 2 of review 1 / Reviewer 2: submission 1.2 cat 2 of review 2 / Reviewer 3: submission 1.3 cat 2 of review 5 |
| 2 | 1 | Reviewer 1: submission 2.1 cat 1 of review 3 / Reviewer 2: submission 2.2 cat 1 of review 7 |
| 2 | 2 | Reviewer 1: submission 2.1 cat 2 of review 3 / Reviewer 2: submission 2.2 cat 2 of review 7 |
| 3 | 1 | Reviewer 1: submission 3.1 cat 1 of review 4 / Reviewer 2: submission 3.2 cat 1 of review 6 / Reviewer 3: submission 3.3 cat 1 of review 8 |
| 3 | 2 | Reviewer 1: submission 3.1 cat 1 of review 4 / Reviewer 2: submission 3.2 cat 2 of review 6 / Reviewer 3: submission 3.3 cat 2 of review 6 |
+---------------+-------------+-----------------------------------------------------------------------------------------------------------------------------------------------+
修复您的查询。
基本问题是表本质上是未排序的，这就是为什么 MySQL 优化器删除了 ORDER BY.
在MySQL中是否足以将所有表放在FROM子句中并使用顺序进行子查询，mysql将保留它。
在 Mariadb 中，这还不够您还添加了一个 LIMIT 18446744073709551615 以便优化器将保留它
架构（MySQL v5.5）
查询#1
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 := @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
(SELECT review_id, submission_id, category_id,`rating` FROM review_detail
LEFT JOIN review ON review.id = review_detail.review_id
ORDER BY review_id, submission_id, category_id ) t1,
(
SELECT
@i := 0,
@grp := ''
) init
GROUP BY
submission_id,
category_id;
结果
| submission_id | category_id | @i | @grp | catgroup | concatText |
| ------------- | ----------- | --- | ---- | -------- | --------------------------------------------------------------------------------------------------------------------------------------------- |
| 1 | 1 | 0 | | 1-1 | Reviewer 3: submission 1.1 cat 1 of review 1 / Reviewer 2: submission 1.2 cat 1 of review 2 / Reviewer 1: submission 1.3 cat 1 of review 5 |
| 1 | 2 | 3 | 1-1 | 1-2 | Reviewer 3: submission 1.1 cat 2 of review 1 / Reviewer 2: submission 1.2 cat 2 of review 2 / Reviewer 1: submission 1.3 cat 2 of review 5 |
| 2 | 1 | 3 | 1-2 | 2-1 | Reviewer 1: submission 2.1 cat 1 of review 3 / Reviewer 2: submission 2.2 cat 1 of review 7 |
| 2 | 2 | 2 | 2-1 | 2-2 | Reviewer 2: submission 2.1 cat 2 of review 3 / Reviewer 1: submission 2.2 cat 2 of review 7 |
| 3 | 1 | 2 | 2-2 | 3-1 | Reviewer 2: submission 3.1 cat 1 of review 4 / Reviewer 1: submission 3.2 cat 1 of review 6 / Reviewer 3: submission 3.3 cat 1 of review 8 |
| 3 | 2 | 3 | 3-1 | 3-2 | Reviewer 3: submission 3.1 cat 1 of review 4 / Reviewer 2: submission 3.3 cat 2 of review 6 / Reviewer 1: submission 3.2 cat 2 of review 6 |
您需要使用 tow-step 子查询按审稿人编号排序。
SET @i := 0;
SET @grp := '';
SELECT
submission_id,
category_id,
GROUP_CONCAT(
CONCAT(
'Reviewer ',
i,
': ',
rating,
' of review ', review_id
)
ORDER BY i
SEPARATOR ' / '
) concatText
FROM
-- second, add numbering
(
SELECT *,
@i := IF(
@grp = @grp := CONCAT_WS('-',submission_id,category_id),
@i + 1, 1) i
FROM
-- first, sort for numbering
(
SELECT
review_id,
submission_id,
category_id,
rating
FROM review_detail LEFT JOIN review ON review.id = review_detail.review_id
ORDER BY
submission_id,
category_id,
review_id
) t1
) t2
GROUP BY
submission_id,
category_id
;
为了完整起见，我还添加了如何在 Mysql 8.0
中完成的解决方案它适用于 COUNT(*)
with base as (
SELECT
review_id,
submission_id,
category_id,
rating,
count(*) over (partition by submission_id,category_id order by review_id) num
FROM review_detail LEFT JOIN review ON review.id = review_detail.review_id
ORDER BY
submission_id,
category_id,
review_id
)
select
submission_id,
category_id,
group_concat(concat('Reviewer', num, ': ', rating, ' of review ', review_id ) separator ', ') concattext
from base
group by
submission_id,
category_id
;
或ROW_NUMBER()
with base as (
SELECT
review_id,
submission_id,
category_id,
rating,
ROW_NUMBER() over (partition by submission_id,category_id order by review_id) num
FROM review_detail
LEFT JOIN review ON review.id = review_detail.review_id
ORDER BY
submission_id,
category_id,
review_id
)
SELECT
submission_id,
category_id,
group_concat(concat('Reviewer', num, ': ', rating, ' of review ', review_id ) separator ', ') concattext
from base
group by
submission_id,
category_id
;