mysql - 我们可以对group_concat(distinct somefield)做一个DISTINCT吗？

http://sqlfiddle.com/#!2/37dd94/17
如果我做SELECT DISTINCT我得到的结果和做SELECT一样。
在查询结果中，您将看到两个包含区域“Evora”的活动。
只能出现一个。
有线索吗？

最佳答案

下面的查询（SQL FIDDLE）如何：

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;

上面的查询将消除额外的Faro和Evora。

关于mysql - 我们可以对group_concat(distinct somefield)做一个DISTINCT吗？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/23544348/