「where」附近的SQL語法錯誤

Question

我是個新手。這可能是一個簡單的解決方法。

查詢：

select AvgR.preavgMR - AvgR.postavgMR 
from (
    ((select R.mID mID, avg(R.stars) preavgMR from Rating R group by R.mID) 
    join Movie M using (mID) 
    where year < 1980 
    ) 
    join  
    ((select R.mID mID, avg(R.stars) postavgMR from Rating R group by R.mID) 
    join Movie M using (mID) 
    where year >= 1980 
    ) 
) AvgR using (mID); 

結果：

Query failed to execute: near "where": syntax error 

/建議的想法？謝謝！

Answer 1

試試這個方法：

select AvgR.preavgMR - AvgR.postavgMR 
from (
    ( 
     select mID,preavgMR 
     from (select R.mID mID, avg(R.stars) preavgMR from Rating R group by R.mID) T1 
     join Movie M using (mID) 
     where year < 1980 
    ) 
    join  
    (
     select mID,postavgMR 
     from (select R.mID mID, avg(R.stars) postavgMR from Rating R group by R.mID) T2 
    join Movie M using (mID) 
    where year >= 1980 
    ) 
) AvgR;