sql - 如何对从 Redshift 中的多个表导入的数据进行过滤和分组？

Question

很高兴认识你，亲爱的社区！我想从几个表中选择自注册日起不迟于 7 天执行最后一次活动的用户，并按他们的开始版本对他们进行分组。

但是，选择的用户数量很少，您能告诉我我哪里出错了吗？

FROM   (SELECT user_id, country, user_creation_time,  event_type, event_time, start_version 
        FROM   PUBLIC.export_07_2020 
        UNION 
        SELECT user_id, country, user_creation_time,  event_type, event_time, start_version
        FROM   PUBLIC.export_08_2020 
        UNION 
        SELECT user_id, country, user_creation_time,  event_type, event_time, start_version
        FROM   PUBLIC.export_09_2020) dat 
WHERE dat.country = 'United States' 
       AND dat.user_creation_time BETWEEN 
           '2020-07-01 00:00:00' AND '2020-09-23 23:59:59' 
      AND NOT EXISTS (SELECT dit.user_id 
                   FROM   (SELECT user_id, 
                                  country, 
                                  user_creation_time, 
                                  event_type, 
                                  event_time 
                           FROM   PUBLIC.export_07_2020 
                           UNION 
                           SELECT user_id, 
                                  country, 
                                  user_creation_time, 
                                  event_type, 
                                  event_time 
                           FROM   PUBLIC.export_08_2020 
                           UNION 
                           SELECT user_id, 
                                  country, 
                                  user_creation_time, 
                                  event_type, 
                                  event_time 
                           FROM   PUBLIC.export_09_2020) dit 
                   WHERE  dat.user_id = dit.user_id 
                          AND Greatest(dit.event_time) > 
                              Dateadd(day, 7, dit.user_creation_time))  
GROUP  BY dat.start_version```