Oracle 21c

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CREATE TABLE stockages (cote) AS
SELECT '200209650304' FROM DUAL UNION ALL
SELECT '200209650301' FROM DUAL UNION ALL
SELECT '200209650302' FROM DUAL UNION ALL
SELECT '2015-2265-02-04' FROM DUAL UNION ALL
SELECT '2015-2265-02-04' FROM DUAL UNION ALL
SELECT '2015-2265-0203' FROM DUAL UNION ALL
SELECT '2015-2265-0202' FROM DUAL;
7 rows affected

UPDATE /*CSL.*/STOCKAGES
SET COTE = REGEXP_REPLACE(
             COTE,
             '(\d{4})-?(\d{4})-?(\d{2})-?(\d{2})',
             '\1-\2-\3\4'
           )
WHERE REGEXP_LIKE(
        COTE,
        '(\d{4})-?(\d{4})-?(\d{2})-?(\d{2})'
      )
AND   NOT REGEXP_LIKE(
        COTE,
        '\d{4}-\d{4}-\d{4}'
      );
5 rows affected

SELECT * FROM stockages;


COTE


2002-0965-0304

2002-0965-0301

2002-0965-0302

2015-2265-0204

2015-2265-0204

2015-2265-0203

2015-2265-0202