条件在MySQL GROUP_CONCAT

Question

我有一个请求

+--------+-------------+-----+ 
| req_id | req_name | ... | 
+--------+-------------+-----+ 
| 1  | testrequest | ... | 
+--------+-------------+-----+ 

一个MySQL表，并与这些请求票表。

+--------+-----------+----------+ 
| req_id | vote_name | approved | 
+--------+-----------+----------+ 
| 1  | User1  | 1  | 
| 1  | User2  | 1  | 
| 1  | User3  | 1  | 
| 1  | User4  | 0  | 
| 1  | User5  | 0  | 
+--------+-----------+----------+ 

那种观点我想：

+--------+-------------+---------------------+--------------+ 
| req_id | req_name | approved_by   | rejected_by | 
+--------+-------------+---------------------+--------------+ 
| 1  | testrequest | User1, User2, User3 | User4, User5 | 
+--------+-------------+---------------------+--------------+ 

然而到目前为止，我只能够做到这一点：

+--------+-------------+----------+---------------------+ 
| req_id | req_name | approved | by     | 
+--------+-------------+----------+---------------------+ 
| 1  | testrequest | YES  | User1, User2, User3 | 
| 1  | testrequest | NO  | User4, User5  | 
+--------+-------------+----------+---------------------+ 

我使用的查询：

SELECT requests.req_id, req_name, CASE 
     WHEN approved THEN 'YES' 
     ELSE 'NO' 
     END AS approved, GROUP_CONCAT(vote_name ORDER BY vote_name ASC SEPARATOR ', ') AS by 
FROM requests 
LEFT JOIN votes ON requests.req_id = votes.req_id 
GROUP BY requests.req_id, approved 
ORDER BY requests.req_id DESC; 

所以我的问题是，我怎么得到2 group_c oncats在同一行中使用不同的值？

非常感谢！

Answer 1

试试这个：

select r.req_id, r.req_name, 
    group_concat(if(approved, vote_name, null) separator ', ') approvedBy, 
    group_concat(if(approved, null, vote_name) separator ', ') rejectedBy 
from requests r 
left join votes v on r.req_id = v.req_id 

结果：

+--------+-------------+---------------------+--------------+ 
| REQ_ID | REQ_NAME |  APPROVEDBY  | REJECTEDBY | 
+--------+-------------+---------------------+--------------+ 
|  1 | testrequest | User1, User2, User3 | User4, User5 | 
+--------+-------------+---------------------+--------------+ 

Answer 2

我试图重新使用另一个查询中查询

SELECT req_id, 
    req_name, 
    GROUP_CONCAT(case approved when 'YES' then voted_by else null end SEPARATOR ', ') AS approved_by, 
    GROUP_CONCAT(case approved when 'NO' then voted_by else null end SEPARATOR ', ') AS rejected_by 
FROM 
(
SELECT requests.req_id, req_name, CASE 
    WHEN approved THEN 'YES' 
    ELSE 'NO' 
    END AS approved, 
    GROUP_CONCAT(vote_name ORDER BY vote_name ASC SEPARATOR ', ') AS voted_by 
FROM requests 
LEFT JOIN votes ON requests.req_id = votes.req_id 
GROUP BY requests.req_id, approved 
ORDER BY requests.req_id DESC 
) t 
group by req_id