题解 | 统计所有课程参加培训人次 逗号数量+1就是这个人培训课程数

select sum(course_count) as staff_nums
from (
    select staff_id,
    case 
        when course is null then 0
        else (length(course) - length(replace(course, ',', '')) + 1)
    end as course_count
    from cultivate_tb
) as a;