mysql - 具有求和函数时查询无法正常运行

Question

我正在运行查询:

select 
    iars.id,students.rollno,
    students.name as name, 
    teachers.name as tname, 
    students.studentid, 
    t1.studentid,
    sum(t1.obt) as obt1, sum(t1.benefits) as ben1, sum(t1.max)  as max1,
    (t2.obt) as obt2, (t2.benefits) as ben2, (t2.max)  as max2,
    (t3.obt) as obt3, (t3.benefits) as ben3, (t3.max)  as max3,
    (t4.obt) as obt4, (t4.benefits) as ben4, (t4.max)  as max4,
    (t5.obt) as obt5, (t5.benefits) as ben5, (t5.max)  as max5 
from groups,students
left join iars on iars.id
left join str on str.studentid=students.studentid
left join course on course.c_id=students.course 
left join teachers on teachers.id=iars.teacherid
join sgm on sgm.studentid=students.studentid
left join semdef on month
left join sps on sps.studentid=students.studentid and iars.paperid=sps.paperid
left join `attndata` `t1` on ((t1.studentid=students.studentid) and iars.id=t1.iarsid and t1.mon=1)
left join `attndata` `t2` on ((t1.studentid=t2.studentid) and t2.mon = 2 and iars.id=t2.iarsid)
left join `attndata` `t3` on ((t2.studentid=t3.studentid) and t3.mon = 4 and iars.id=t3.iarsid)
left join `attndata` `t4` on ((t3.studentid=t4.studentid) and t4.mon = 5 and iars.id=t4.iarsid)
left join `attndata` `t5` on ((t4.studentid=t5.studentid) and t5.mon = 6 and iars.id=t5.iarsid)
where students.course='1' and students.status='regular' and sps.paperid='2' and 
iars.courseid=students.course and iars.semester=str.semesterid and iars.paperid='2' and
str.semesterid='1' and str.sessionid='12' and groups.id=sgm.groupid 
group by sps.studentid , teachers.id order by students.name

它是分组的，就像我想根据月份求和，但每当我使用 sum 时，它都会给我带来有趣的结果。

Answer 1

如果您想要按月份求和，您应该按日期和月份分组。与学生和老师分组将使您每月多于一行，并会导致有趣的结果