SQL Server 2022

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CREATE TABLE salesorders (
    region VARCHAR(100),
    unit INT
)
INSERT INTO salesorders
VALUES
    ('East', 5),
    ('East', 15),
    ('West', 50),
    ('East', 5),
    ('West', 10)
5 rows affected

with region_sums as
(
    select region, sum(unit) Sum_unit
    from salesorders 
    group by region
) 
select
    rs.region,
    rs.Sum_unit,
    100e0 * rs.Sum_unit / sum(rs.Sum_unit) over() as Percentage 
from region_sums rs


region
Sum_unit
Percentage


East
25
29.4117647058824

West
60
70.5882352941177


select
    rs.region,
    rs.Sum_unit,
    100e0 * rs.Sum_unit / sum(rs.Sum_unit) over() as Percentage 
from (
    select s.region, sum(s.unit) Sum_unit
    from salesorders s
    group by s.region
) rs


region
Sum_unit
Percentage


East
25
29.4117647058824

West
60
70.5882352941177


select
    s.region,
    sum(s.unit) Sum_unit,
    100e0 * sum(s.unit) / sum(sum(s.unit)) over() as Percentage
from salesorders s
group by s.region


region
Sum_unit
Percentage


East
25
29.4117647058824

West
60
70.5882352941177