你描述的问题不清楚,但可以这么试试看
select student_id,student_area,count(*)
from tab
group by student_id,student_area;
或者
select student_id,max(student_area),count(*)
from tab
group by student_id;
select student_id,student_area,count(*)
from tab
group by student_id,student_area;
或者
select student_id,max(student_area),count(*)
from tab
group by student_id;
解决方案 »
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