Mysql 查询不工作并显示错误

Question

我正在开发学生出勤系统并尝试执行此查询:

select s.full_name,
   s.student_id,
   count(a.id) as total_present,
   count(CASE WHEN TIMEDIFF(min(a.punch_in_time),'10:00:00') THEN '1' END)  'late'
from student s, attendance_record a 
where  a.student_id=s.student_id 
  and a.punch_in_date BETWEEN '2018-12-26' and '2018-12-26'
group by s.student_id

但这总是显示错误“无效使用组功能”

我找不到任何错误。请帮助我。

Answer 1

在分组依据中，您必须放置ALL 非聚合列:

select s.full_name,
   s.student_id,
   count(a.id) as total_present,
   count(CASE WHEN TIMEDIFF(min(a.punch_in_time),'10:00:00') THEN '1' END)  'late'
from student s, attendance_record a 
where  a.student_id=s.student_id 
  and a.punch_in_date BETWEEN '2018-12-26' and '2018-12-26'
group by s.student_id , s.full_name

注意:最好用“LEFT JOIN”或“INNER JOIN”来连接表，因为它更具可读性

select s.full_name,
   s.student_id,
   count(a.id) as total_present,
   count(CASE WHEN TIMEDIFF(min(a.punch_in_time),'10:00:00') THEN '1' END)  'late'
from student s
INNER JOIN attendance_record a ON  a.student_id=s.student_id 
where 
   a.punch_in_date BETWEEN '2018-12-26' and '2018-12-26'
group by s.student_id , s.full_name