我们可以对group_concat(distinct somefield)做一个DISTINCT吗? [英] Can we make a DISTINCT of a group_concat(distinct somefield)?

问题描述

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

如果执行SELECT DISTINCT，我得到的结果与SELECT相同.

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

在查询结果上，您将看到两个包含"Evora"区的活动. 应该只出现一个.

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

有任何线索吗?

推荐答案

以下查询如何处理(

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;

上面的查询将消除多余的Faro和Evora.

The above query will eliminate the extra Faro and Evora.

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