Recursive maximise sum, Oracle

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--Oracle 11g Express Edition
--please drop objects you've created at the end of the script 
--or check for their existance before creating
--'\\' is a delimiter

with tbl(key, value) as (
    select 'A',  1 from dual union all
    select 'B',  2 from dual union all
    select 'C',  3 from dual union all
    select 'D', 99 from dual union all
    select 'E', 90 from dual
),
rec(greatest_key, greatest_single, key_count, keys, total) as (
    select     key,
               value,
               1,
               key, 
               value
    from       tbl
    union all
    select     tbl.key,
               greatest(tbl.value, rec.greatest_single),
               rec.key_count+1,
               substr(rec.keys, 0, 1000) || ', ' || tbl.key,
               rec.total + tbl.value
    from       rec 
    inner join tbl 
            on tbl.key > rec.greatest_key
           and rec.total + tbl.value <= 102
),
ordered(total, keys, r) as (
    select   total, keys, row_number() over (order by total desc, key_count desc, greatest_single desc)
    from     rec
)
select total, keys
from   ordered
where  r = 1
\\


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