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Question

使用GROUP_CONCAT這裏有一個我的數據庫結構的圖片：使用GROUP_CONCAT一個非常複雜的SQL語句

隨着從這裏用戶的幫助，我已經成功地放在一起：

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"; 

這似乎工作正常，除了Focus,Positive和Development各自重複取決於具有最高concat數的字段enations英寸

例如，如果Positive有Pace,Progress,Attainment但Focus只有Appraisal，它會被重複三次（Appraisal,Appraisal,Appraisal）。

我看這件事，我認爲這可能是因爲我需要GROUP這些GROUP_CONCAT JOINs的。但是，我不知道如何去做這件事。

任何人都可以幫忙嗎？在此先感謝，

Answer 1

GROUP_CONCAT具有可用於刪除重複項的DISTINCT屬性。

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";