Oracle 21c

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CREATE TABLE t(nameid_p VARCHAR2(25),name_id INT, product_id INT)
INSERT INTO t(nameid_p) 
SELECT '123_456' FROM dual UNION ALL
SELECT '653_857' FROM dual UNION ALL
SELECT '5633_85' FROM dual
3 rows affected

UPDATE t
   SET name_id = REGEXP_SUBSTR(nameid_p,'[^_]+'),
       product_id = REGEXP_SUBSTR(nameid_p,'[^_]+$')
3 rows affected

SELECT * FROM t


NAMEID_P
NAME_ID
PRODUCT_ID


123_456
123
456

653_857
653
857

5633_85
5633
85