postgresql – 从查询更新Redshift表

update mr_usage_au au
inner join(SELEct mr.UserID,date(mr.ActionDatE) as ActionDate,count(case when mr.EventID in (32) then mr.UserID end) as Moods,count(case when mr.EventID in (33) then mr.UserID end) as ActivitIEs,sum(case when mr.EventID in (10) then mr.Duration end) as Duration
           from   mr_session_log mr
           where  mr.EventTime >= current_date - interval '1 days' and mr.EventTime < current_date
           Group By mr.UserID,date(mr.ActionDatE)) slog on slog.UserID=au.UserID
                                             and slog.ActionDate=au.Date
set au.Moods = slog.Moods,au.ActivitIEs=slog.ActivitIEs,au.Durarion=slog.Duration

对于Redshift(或POSTGRes),这是完全无效的语法.让我想起了sql Server ……

应该这样工作(至少在目前的POSTGRes上)：

updatE mr_usage_au
SET    Moods = slog.Moods,ActivitIEs = slog.ActivitIEs,Durarion = slog.Duration       
FROM (
   SELEct UserID,ActionDate::date,count(CASE WHEN EventID = 32 THEN UserID END) AS Moods,count(CASE WHEN EventID = 33 THEN UserID END) AS ActivitIEs,sum(cASE WHEN EventID = 10 THEN Duration END) AS Duration
   FROM   mr_session_log
   WHERE  EventTime >= current_date - 1  -- just subtract Integer from a date
   AND    EventTime <  current_date
   GROUP  BY UserID,ActionDate::date
   ) slog
WHERE slog.UserID = mr_usage_au.UserID
AND   slog.ActionDate = mr_usage_au.Date;

POSTGRes和Redshift通常就是这种情况：

>使用FROM子句连接其他表.
>您不能在SET子句中对目标列进行表限定.

还有,Redshift was forked from POSTGReSQL 8.0.2,这是很久以前的事了.只应用了POSTGRes的一些后续更新.

>例如,POSTGRes 8.0 did not allow a table alias in an updatE statement,yet – 这就是你看到的错误背后的原因.

我简化了其他一些细节.