返回NULL的MySQL CASE LEFT JOINS

Question

我有一个CASE语句的查询来确定变量object_name该变量来自x_ambitions表或x_trybes表。下面的查询被合并，以便我可以通过执行一个SQL查询来简化它。

我把SELECT语句分成了两个，这样你就可以更好地理解了。下面的两个查询。工作并从数据库中提取正确的object_name。

当我组合两个查询时遇到的问题是'new_join_ambition','new_created_ambition','new_liked_ambition' object_name在LEFT JOIN中返回NULL。

在合并查询中，如果我带上'new_join_ambition','new_created_ambition','new_liked_ambition'以上的案例'new_join_trybe','new_created_trybe','new_liked_trybe'。恰恰相反。 trybe行返回NULL。

两个SQL查询：

答：（检索对象A）

SELECT 
    s.id, 
    s.object_id, 
    s.type, 
    s.postee_id, 
    s.user_id, 
    s.text, 
    s.registered, 
    CONCAT(u.x_first_name,' ',u.x_last_name) AS postee_name, 
    ui.image_id AS postee_image_id, 
    CASE s.type 
     WHEN 'new_join_ambition' 
      OR 'new_created_ambition' 
      OR 'new_liked_ambition'   
      THEN a.name 
      ELSE 'a' 
    END AS object_name 
FROM 
    x_share s 
LEFT JOIN 
    x_user u ON u.id = s.postee_id 
LEFT JOIN 
    x_user_images ui ON ui.user_id = s.postee_id 
LEFT JOIN 
    x_ambitions a ON s.type IN ('new_join_ambition', 'new_created_ambition', 'new_liked_ambition') AND s.object_id = a.id 
LEFT JOIN 
    x_ambition_invites ai ON s.type IN ('new_join_ambition') AND s.object_id = ai.ambition_id AND s.postee_id = ai.to 
LEFT JOIN 
    x_ambition_likes al ON s.type IN ('new_liked_ambition') AND s.object_id = al.ambition_id AND s.postee_id = al.profile_id 
LEFT JOIN 
    x_ambition_owner aoo ON s.type IN ('new_created_ambition') AND s.object_id = aoo.ambition_id 
WHERE 
    s.user_id = '%s' 
ORDER BY 
    s.registered DESC 

B：（检索对象B）

SELECT 
    s.id, 
    s.object_id, 
    s.type, 
    s.postee_id, 
    s.user_id, 
    s.text, 
    s.registered, 
    CONCAT(u.x_first_name,' ',u.x_last_name) AS postee_name, 
    ui.image_id AS postee_image_id, 
    CASE s.type 
     WHEN 'new_join_trybe' 
      OR 'new_created_trybe' 
      OR 'new_liked_trybe' 
      THEN t.name 
      ELSE 'a' 
    END AS object_name 
FROM 
    x_share s 
LEFT JOIN 
    x_user u ON u.id = s.postee_id 
LEFT JOIN 
    x_user_images ui ON ui.user_id = s.postee_id 
LEFT JOIN 
    x_trybes t ON s.type IN ('new_join_trybe', 'new_created_trybe', 'new_liked_trybe') AND s.object_id = t.id 
LEFT JOIN 
    x_trybe_invites ti ON s.type IN ('new_join_trybe') AND s.object_id = ti.trybe_id AND s.postee_id = ti.to 
LEFT JOIN 
    x_trybes_likes tl ON s.type IN ('new_liked_trybe') AND s.object_id = tl.trybe_id AND s.postee_id = tl.profile_id 
LEFT JOIN 
    x_trybe_owner too ON s.type IN ('new_created_trybe') AND s.object_id = too.trybe_id 
WHERE 
    s.user_id = '%s' 
ORDER BY 
    s.registered DESC 

我已经跑了两个查询，并有捕获两个查询结果的图像。

设置A：

集B：

我怎样才能将二者结合起来，而不OBJECT_NAME返回NULL？如果您有任何问题，请使用评论，我会毫不犹豫地回复。

在此先感谢

Answer 1

我不知道您的查询的休息，但你case说法是不正确。您有：

(CASE s.type 
      WHEN 'new_join_ambition' OR 'new_created_ambition' OR 'new_liked_ambition' 
      THEN a.name 
      ELSE 'a' 
END) AS object_name 

的OR s结尾了治疗的值作为数字，所以这相当于WHEN 0 THEN . . .。

你想要的是这种形式的case的：

(CASE WHEN s.type IN ('new_join_ambition', 'new_created_ambition', 'new_liked_ambition') 
     THEN a.name 
     ELSE 'a' 
END) AS object_name