使用GROUP_CONCAT重复值而不使用带有多个连接的MySQL查询的DISTINCT

Question

我有一个类似下面的模式，我尝试进行查询以从单个项目中获取所有过滤器和所有project_items，以便使用GROUP_CONCAT将结果放在一行中。

过滤器

• ID
• 标题

project_filters

• ID
• filters_id
• projects_id

项目

• ID
• 标题

project_items

• ID
• 标题
• projects_id

表格如此连接

[filters] 1 - N [project_filters] N - 1 [项目] 1 - N [project_items]

查询和问题

• 选择
• projects.id，
• projects.title，
• GROUP_CONCAT（project_items.title）AS items_title，
• GROUP_CONCAT（filters.title）AS filters_title
• FROM projects
• LEFT JOIN project_items ON project_items.projects_id = projects.id
• LEFT JOIN project_filters ON projects.id = project_filters.projects_id
• LEFT JOIN过滤器过滤器.id = project_filters.filters_id
• WHERE projects.id =＆＃34; 1＆＃34;

项目1有3个过滤器（1,2和3）和3个项目（1,2和3），这导致重复值（每个9个），如下所示：

• id = 1
• title = project 1
• items_title = title 1，title 2，title 3，title 1，title 2，title 3，title 1，title 2，title 3
• filters_title =过滤器1，过滤器2，过滤器3，过滤器1，过滤器2，过滤器3，过滤器1，过滤器2，过滤器3

有人能指出我正确的方向吗？我想知道如何使查询返回过滤器和项而不重复。

我认为解决方案是以某种方式安排联接，但我无法弄明白。

OBS：带有DISTINCT的GROUP_CONCAT不适合，因为可能会有重复的标题

非常感谢！

Answer 1

好的，通过@cha的答案（感谢队友）和更多的研究，我通过删除两个查询之间的INNER JOIN得到了正确的结果。

SELECT i.id, i.title, i.items_title, f.filters_title FROM
( SELECT
  projects.id,
  projects.title,
  GROUP_CONCAT(project_items.title) AS items_title
  FROM projects
  LEFT JOIN project_items ON project_items.projects_id=projects.id
  WHERE projects.id="1"
  GROUP BY projects.id) AS i,
( SELECT
  projects.id,
  projects.title,
  GROUP_CONCAT(filters.title) AS filters_title
  FROM projects
  LEFT JOIN project_filters ON projects.id=project_filters.projects_id
  LEFT JOIN filters ON filters.id=project_filters.filters_id
  WHERE projects.id="1"
  GROUP BY projects.id) AS f
WHERE i.id=f.id

Answer 2

为每个GROUP_CONCAT使用子查询：

SELECT i.id, i.title, i.items_title, f.filters_title FROM
( SELECT
  projects.id,
  projects.title,
  GROUP_CONCAT(project_items.title) AS items_title
  FROM projects
  LEFT JOIN project_items ON project_items.projects_id=projects.id
  group by projects.id,
  projects.title) as i
INNER JOIN
( SELECT
  projects.id,
  projects.title,
  GROUP_CONCAT(filters.title) AS filters_title
  FROM projects
  LEFT JOIN project_filters ON projects.id=project_filters.projects_id
  LEFT JOIN filters ON filters.id=project_filters.filters_id
  group by projects.id,
  projects.title) as f
ON i.id = f.id
WHERE i.id="1"