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