题解 | 统计所有课程参加培训人次

select sum(course1)+sum(course2)+sum(course3) as staff_nums
from
(select info_id,staff_id,if(course like '%1%',1,0) as course1,if(course like '%2%',1,0) as course2,if(course like '%3%',1,0) as course3
from cultivate_tb
where course is not Null) as t