mysql - 错误代码：1111. 组函数使用无效 MYSQL ERROR

Question

我正在尝试查找低于课程平均成绩的学生名单

我有这个查询

Select studentName 
from courseGrade 
where grade < avg(grade) and sectionID=290001

Answer 1

使用子查询来计算课程的平均成绩。例如：

select studentName 
from courseGrade 
where sectionID = 290001
  and grade < (
    select avg(grade) from courseGrade where sectionID = 290001
  )