使用 SQL 为行分配加权值

Question

I have a table of customers that I want to assign a test group. I want to assign a test group based on weighted values.

Example:

Group 1 - 50%
Group 2 - 25%
Group 3 - 20%
Group 4 - 5%

Result:

customer_id	group
1	group 1
2	group 4
3	group 1
4	group 2
5	group 1
6	group 1
7	group 2
8	group 1
9	group 3
10	group 1

Answer 1

If you shuffle the rows randomly you can then split based on the cumulative frequencies. While this works neatly the fractions are neat I'm not sure if this will meet the most general case you've got.

with data as (
    select *,
        count(*) over () * 1.0 as cnt,
        row_number() over (order by random()) * 1.0 as rn
    from T
)
select customer_id,
    case when rn / cnt <= 0.50 then 'Group 1'
         when rn / cnt <= 0.75 then 'Group 2'
         when rn / cnt <= 0.95 then 'Group 3'
         when rn / cnt <= 1.00 then 'Group 4'
    end as grp
from data;