题解 | 统计所有课程参加培训人次

select 
    number1+number2+number3 as staff_nums
from (
    select 
        sum(case  when course like '%1%' then 1 else 0 end ) as number1,
        sum(case  when course like '%2%' then 1 else 0 end ) as number2,
        sum(case  when course like '%3%' then 1 else 0 end ) as number3
    from cultivate_tb
) temp ;