Question

我有一个表hostapp_apps和一个带有列的视图host_app_usercount，如下所示

 hostapp_apps  
======================================================       
 host_app_id || app_type || app_id || platform || user_count

host_app_usercount
======================================================
host_id || TotalUsers

基本上我试图通过使用以下查询来获取app_id，platform，max（usercount），TotalUsers

 SELECT hostapp_apps.app_type as app_type, host_app_usercount.TotalUsers as Total,
        hostapp_apps.app_id as app_id, MAX(hostapp_apps.user_count) AS sum,
        ROUND((MAX(hostapp_apps.user_count)/(host_app_usercount.TotalUsers) * 100 ),2) AS percentage
FROM pg_datascience.hostapp_apps LEFT OUTER JOIN
     host_app_usercount
     ON (host_app_usercount.host_id=hostapp_apps.host_app_id)
GROUP BY hostapp_apps.app_id, host_app_usercount.TotalUsers
HAVING sum >= 10000
ORDER BY percentage desc
limit 0, 50;

但获取数据需要很长时间。有没有办法在没有左外连接的情况下执行此操作。另外，我尝试了另一种方法，不使用连接

SELECT hostapp_apps.app_type as app_type,
       (select TotalUsers
        from host_app_usercount
        where host_app_usercount.host_id=hostapp_apps.host_app_id
       ) as Total,
       hostapp_apps.app_id as app_id, MAX(hostapp_apps.user_count) AS sum, 
       ROUND((MAX(hostapp_apps.user_count)/(Total) * 100 ),2) AS percentage
 FROM pg_datascience.hostapp_apps
 GROUP BY hostapp_apps.app_id, Total
 HAVING sum >= 10000
 ORDER BY percentage desc
 limit 0, 50;

但是当我尝试这个时，我在字段列表中得到了未知的列'Total'。任何帮助都非常感谢，因为它影响了我的任务进度:(提前致谢

Answer 1

首先，您的第一个查询无效。您的列app_type不是聚合，不在Group By子句中。该查询将给您一个错误。

其次，它可能是一个索引问题。您需要查看索引并可能创建它们。我会在以下各项中创建一个：

host_app_usercount.host_id

hostapp_apps.host_app_id

这应该有所帮助。

使用左外连接获取数据需要更多时间

1 个答案: