mysql - 在多个字段上使用 GROUP_CONCAT

Question

这是我的数据库结构的图片:

在此处用户的帮助下，我成功地使用 GROUP_CONCAT 组合了相当复杂的 SQL 语句:

SELECT
     t1.Name AS Teacher_Name,
     t2.Name AS Observer_Name,
     o.Datetime AS Datetime,
     o.Type AS Type,
     o.Year_Group AS Year_Group,
     o.Class_Name AS Class_Name,
     c.Title AS Course_Name,
     GROUP_CONCAT(l.Title) AS Focus,
     o.Achievement_Grade AS Achievement_Grade,
     o.Behaviour_Grade AS Behaviour_Grade,
     o.Teaching_Grade AS Teaching_Grade,
     GROUP_CONCAT(cl1.Title) AS Positive,
     GROUP_CONCAT(cl2.title) AS Development,
     o.Notes AS Notes
FROM observations o
LEFT JOIN teachers t1 
    ON o.Teacher_ID = t1.Teacher_ID
LEFT JOIN teachers t2 
    ON o.Observer_ID = t2.Teacher_ID
LEFT JOIN courses c 
    ON o.Course_ID = c.Course_ID
LEFT JOIN  foci f
    ON o.ID = f.Observation_ID
LEFT JOIN focus_labels l
    on f.focus_id = l.id
LEFT JOIN  criteria c1
    ON o.ID = c1.Observation_ID
LEFT JOIN criteria_labels cl1
    on c1.Criteria_ID = cl1.ID AND c1.Type = 'P'
LEFT JOIN  criteria c2
    ON o.ID = c2.Observation_ID AND c2.Type = 'D'
LEFT JOIN criteria_labels cl2
    on c2.Criteria_ID = cl2.ID
GROUP BY o.id
ORDER BY `Datetime` DESC";

这似乎工作正常，除了 Focus、Positive 和 Development 分别根据具有最多的串联数。

例如，如果Positive具有Pace、Progress、Attainment，但Focus只是Appraisal，那么它'将重复三次(评估，评估，评估)。

我查了一下，我认为这可能是因为我需要对每个 GROUP_CONCAT JOIN 进行GROUP。但是，我不知道该怎么做。

有人可以帮忙吗？提前致谢，

Answer 1

GROUP_CONCAT具有可用于删除重复项的 DISTINCT 属性。

SELECT
     t1.Name AS Teacher_Name,
     t2.Name AS Observer_Name,
     o.Datetime AS Datetime,
     o.Type AS Type,
     o.Year_Group AS Year_Group,
     o.Class_Name AS Class_Name,
     c.Title AS Course_Name,
     GROUP_CONCAT(DISTINCT l.Title) AS Focus,
     o.Achievement_Grade AS Achievement_Grade,
     o.Behaviour_Grade AS Behaviour_Grade,
     o.Teaching_Grade AS Teaching_Grade,
     GROUP_CONCAT(cl1.Title) AS Positive,
     GROUP_CONCAT(cl2.title) AS Development,
     o.Notes AS Notes
FROM observations o
LEFT JOIN teachers t1 
    ON o.Teacher_ID = t1.Teacher_ID
LEFT JOIN teachers t2 
    ON o.Observer_ID = t2.Teacher_ID
LEFT JOIN courses c 
    ON o.Course_ID = c.Course_ID
LEFT JOIN  foci f
    ON o.ID = f.Observation_ID
LEFT JOIN focus_labels l
    on f.focus_id = l.id
LEFT JOIN  criteria c1
    ON o.ID = c1.Observation_ID
LEFT JOIN criteria_labels cl1
    on c1.Criteria_ID = cl1.ID AND c1.Type = 'P'
LEFT JOIN  criteria c2
    ON o.ID = c2.Observation_ID AND c2.Type = 'D'
LEFT JOIN criteria_labels cl2
    on c2.Criteria_ID = cl2.ID
GROUP BY o.id
ORDER BY `Datetime` DESC";