MySQL错误-＃1242-子查询返回多于1行

Question

我一直在尝试更新MySQL表中的值，并且通过运行下面的代码遇到此错误。帮助。

UPDATE overall
SET Total_Score  = (
SELECT (
       ot.Total_Score + op.Total_Score
       ) AS Total_Score
FROM (
   SELECT StudentID, Total_Score
   FROM term2
   GROUP BY StudentID
  ) AS ot
INNER JOIN (
       SELECT StudentID, Total_Score
       FROM overall
       GROUP BY StudentID
     ) AS op ON ( op.StudentID = ot.StudentID )
)