题解 | 统计所有课程参加培训人次

select 
    sum(label_1)+sum(label_2)+sum(label_3) as staff_nums
from 
(
    select 
    info_id,
    staff_id,
    course,
	#为每个课程打标
    case 
            when course like '%1%' then 1
            else 0
        end as label_1,
        case 
            when course like '%2%' then 1
            else 0
        end as label_2,
        case 
            when course like '%3%' then 1
            else 0
        end as label_3
    from cultivate_tb
) t