Question

我是个新手。这可能很容易解决。

查询：

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);

结果：

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

思想/建议？谢谢！

Answer 1

尝试这种方式：

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;

“where”附近的SQL语法错误

1 个答案: