with s as (
select 'DL:2212200090001 Pr:8222046017'  str from dual union all
select 'Obj:020220215541 DL:1099089729'  str from dual union all
select 'DL:DST22017260'                  str from dual union all
select 'DL:22122000123964 Pr:8222062485' str from dual union all
select 'DL:22122000108599'               str from dual union all
select 'Obj:0202200015539 DL:2100001688' str from dual)
select str, regexp_substr(str, 'DL:(\S+)', 1, 1, null, 1) rs
from s;

STR                             RS
------------------------------- -------------------------------
DL:2212200090001 Pr:8222046017  2212200090001
Obj:020220215541 DL:1099089729  1099089729
DL:DST22017260                  DST22017260
DL:22122000123964 Pr:8222062485 22122000123964
DL:22122000108599               22122000108599
Obj:0202200015539 DL:2100001688 2100001688

6 rows selected

像这样的东西？
示例数据：

SQL> with test (col) as
  2    (select
  3  '________________________________________
  4  DL:2212200090001 Pr:8222046017
  5  ________________________________________
  6  Obj:020220215541 DL:1099089729
  7  ________________________________________
  8  DL:DST22017260
  9  ________________________________________
 10  DL:22122000123964 Pr:8222062485
 11  ________________________________________
 12  DL:22122000108599
 13  ________________________________________
 14  Obj:0202200015539 DL:2100001688'
 15  from dual)
 16  --

查询：

17  select replace(regexp_substr(col, 'DL:\w+', 1, level), 'DL:') result
 18  from test
 19  connect by level <= regexp_count(col, 'DL:');

RESULT
--------------------------------------------------------------------------------
2212200090001
1099089729
DST22017260
22122000123964
22122000108599
2100001688

6 rows selected.

SQL>

(note如果您要处理的数据不止一行，则可能需要修改该查询）

You could achieve this by using regular expressions utilising a positive lookbehind and lookahead.
The regex (?<=DL\:)\d*(?=\s)' matches all digits between DL: until a single whitespace character occurs.
You'd want to use the REGEXP_SUBSTR function for this (as you tagged this question with OracleSQL):

SELECT
  REGEXP_SUBSTR(my_column,
                '(?<=DL\:)\d*(?=\s)') "DL field"
  FROM my_table;

If you want to match substrings like DST22017260 as well, using . (any character) instead of \d would work: (?<=DL\:).*(?=\s) .