我们可以对 group_concat(distinct somefield) 进行 DISTINCT 吗?

Can we make a DISTINCT of a group_concat(distinct somefield)?(我们可以对 group_concat(distinct somefield) 进行 DISTINCT 吗?)

问题描述

http://sqlfiddle.com/#!2/37dd94/17

如果我执行 SELECT DISTINCT，我会得到与仅执行 SELECT 相同的结果.

If I do SELECT DISTINCT I get the same results as doing just SELECT.

在查询结果中，您将看到两个包含Evora"区的活动.只有一个应该出现.

On the query results, you will see two activities that contains the District "Evora". Only one should appear.

有什么线索吗?

推荐答案

下面的查询怎么样 (SQL FIDDLE):

How about the following query (SQL FIDDLE):

SELECT GROUP_CONCAT(APA_T.district), t.name
FROM tbl_activity AS t 
JOIN tbl_activity_package AS ap ON t.id = ap.id_activity 
JOIN 
(
  SELECT DISTINCT apa.district AS district, 
  (
     SELECT s1.id_activity_package 
     FROM tbl_activity_package_address s1
     WHERE apa.district = s1.district
     ORDER BY s1.id DESC
     LIMIT 1
  ) AS idActivityPackage
  FROM 
  tbl_activity_package_address apa
  ORDER BY apa.district
) AS APA_T
ON ap.id = APA_T.idActivityPackage
GROUP BY t.name 
ORDER BY APA_T.district;

上面的查询会去掉多余的Faro和Evora.

The above query will eliminate the extra Faro and Evora.

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