错误代码：1242子查询返回多于1行

Question

有问题，我正在尝试计算每个员工的Total_Hours，但是在分组时会出现错误。但是，我知道问题是什么，但我不知道如何解决它。

Select
    tt.uid as 'Employee',
    if (tc.organisation like '%Village%' or tc.organisation like '%Personnel%', 'Village', 'Client' ) as 'Type of work',
    round((sum(timestampdiff(minute, start_time, end_time))/60),2) AS 'Hours',
    (select 
        round((sum(timestampdiff(minute, start_time, end_time))/60),2)
    from timesheet.timesheet_times ttt
        left outer join timesheet.timesheet_project ttp on ttt.proj_id = ttp.proj_id
        left outer join timesheet.timesheet_client ttc on ttp.client_id = ttc.client_id
    where   
        month(ttt.start_time) = month(now())
        and year(ttt.start_time) = year(now())
group by
        ttt.uid 
     )as TOTAL_HOURS_PER_EMPLOYEE,
    round((
    (round((sum(timestampdiff(minute, start_time, end_time))/60),2)
    /
    (select 
        round((sum(timestampdiff(minute, start_time, end_time))/60),2)
    from timesheet.timesheet_times ttt
        left outer join timesheet.timesheet_project ttp on ttt.proj_id = ttp.proj_id
        left outer join timesheet.timesheet_client ttc on ttp.client_id = ttc.client_id
    where   
        month(ttt.start_time) = month(now())
        and year(ttt.start_time) = year(now()))
    )*100),0) as percentage
from
    timesheet.timesheet_times tt
    left outer join timesheet.timesheet_project tp on tt.proj_id = tp.proj_id
        left outer join timesheet.timesheet_client tc on tp.client_id = tc.client_id
where
    month(tt.start_time) = month(now())
    and tc.organisation not like '%Private%'
    and year(tt.start_time) = year(now())

group by
    tc.client_id

order by
    round((sum(timestampdiff(minute, start_time, end_time))/60),2) desc

如果我写错了帖子，我很抱歉，这是我第一次来这里或寻求帮助。