子查询返回1行以上

Question

I have this query:

UPDATE student_info 
    set grade = (SELECT tempTable.grade 
                     FROM tempTable
                     WHERE student_info.s_id = (SELECT s_id FROM tempTable))

I've also tried the suggested solution here: http://dev.mysql.com/doc/refman/5.0/en/subquery-errors.html

Answer 1

I guess you want:

UPDATE student_info 
  JOIN tempTable
    ON tempTable.s_id = student_info.s_id 
SET student_info.grade = tempTable.grade 

Answer 2

Your subquery is returning more than one row, possibly because the JOIN is incorrect. Try:

UPDATE student_info 
    SET grade = (SELECT grade 
         FROM tempTable
         WHERE s_id = student_info.s_id)

This of course assumes that tempTable only contains one record per s_id . If there are more that one then you need to take the TOP 1 ordered by some attribute (latest? highest?)