总计总小时数并按小时分组

Question

I want to group by all the hours between 0 and 40 into one total sum. 41 - 50 into one total sum and 50+ into another sum.

select hours,
       sum(hours)
from   employee
where  hours between 0 and 40
group by hours;

The above query groups by the hours, so i have the results split by hours, like if I have 1, 2.3, 0.5, 35.5, 30 etc.

1       403
2.3     4.6
0.5     53
35.5    284
30      1230

But I want something like 403+4.6+53+284+1230 = 1974.6 because they all fall under 40 How can I do it ?

Answer 1

You can use a conditional aggregation, grouping by a value that builds intervals of hours. By your example, you can have not integer values, so you should use explicit relational operators to have, for example, 40.1 in 40-50 group:

select sum(hours),
       case
          when hours <= 40 then '0-40'
          when hours > 40 and hours <= 50 then '41-50'
          when hours > 50 then '50-...'
         end
from employee
group by case
          when hours <= 40 then '0-40'
          when hours > 40 and hours <= 50 then '41-50'
          when hours > 50 then '50-...'
         end

Answer 2

select sum(case when hours between 0 and 40 then hours else 0 end) hours_1,
       sum(case when hours between 41 and 50 then hours else 0 end) hours_41,
       sum(case when hours > 50 then hours else 0 end) hours_51
from employee 

Answer 3

GROUP -ing based on CASE

select (case when hours between 0 and 40
              then '0 - 40'
              when hours between 41 and 50
              then '41 - 50'
              else
                   '50+'
          end) as hours_range,
        sum(hours) 
from employee
group by (case when hours between 0 and 40
              then '0 - 40'
              when hours between 41 and 50
              then '41 - 50'
              else
                   '50+'
          end);

Answer 4

select '1 to 40',sum(hours)

from   employee
where  hours between 0 and 40

union all

  select '41 to 50',sum(hours)

from   employee
where  hours between 41 and 50

union all

  select '50+',sum(hours)

from   employee
where  hours>50