在一种编程语言中，你可以写一个循环，并通过迭代数日来计算小时数。在sql中，可以对递归查询执行相同的操作：

with recursive cte (id, dt, minutes) as
(
  select
    id,
    date(created_at),
    case
      when dayofweek(created_at) in (1, 7) then 0
      else timestampdiff(minute, created_at, least(now(), date(created_at) + interval 1 day))
    end
  from mytable
  union all
  select
    id,
    dt + interval 1 day,
    case
      when dayofweek(dt + interval 1 day) in (1, 7) then 0
      else timestampdiff(minute, dt + interval 1 day, least(now(), dt + interval 2 day))
    end
  from cte
  where dt + interval 1 day <= curdate()
)
select id, round(sum(minutes) / 60, 1) as hours
from cte
group by id
order by id;

演示：https://dbfiddle.uk/?rdbms=mysql_8.0&fiddle=a08f96bc29fb8a51302da10679496e22