select time_slot_id, MAX(student_num) as max_num
from (select COUNT(takes.ID)as student_num, time_slot_id
from takes, section
where takes.course_id=section.course_id
group by time_slot_id) as num_slot(student_num, time_slot_id);
刚学SQL的菜鸟,这地方老报错,不知道为什么,求各位大神解释
from (select COUNT(takes.ID)as student_num, time_slot_id
from takes, section
where takes.course_id=section.course_id
group by time_slot_id) as num_slot(student_num, time_slot_id);
刚学SQL的菜鸟,这地方老报错,不知道为什么,求各位大神解释
from (
select COUNT(takes.ID)as student_num, time_slot_id
from takes, section
where takes.course_id=section.course_id
group by time_slot_id
) as num_slot
group by time_slot_id
from takes, section
where takes.course_id=section.course_id
group by time_slot_id
order by student_num desc
group by 的语法规则就是所有查询结果不是聚集函数的项都要出现在group by 中
建议给出表数据和期望结果。