Oracle 23c

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

WITH regex_string AS (

SELECT '123456789' AS val FROM dual UNION ALL

SELECT '21-34-567' FROM dual UNION ALL

SELECT '2150-X1234-YZ' FROM dual UNION ALL

SELECT '21-22-93-001' FROM dual

)

SELECT SUBSTR(REGEXP_REPLACE(val, '[^0-9]+', ''), -4) AS last_four

FROM regex_string;