WITH cou AS (
	SELECT 'Jean' AS col1, 'Claude' AS col2, NULL AS col3, NULL as col4 FROM DUAL
	UNION
	SELECT 'Laurent' AS col1, NULL AS col2, NULL AS col3, NULL as col4 FROM DUAL
	UNION
	SELECT NULL AS col1, 'Sylvain' AS col2, NULL AS col3, NULL as col4 FROM DUAL
	UNION 
	SELECT NULL AS col1, NULL AS col2, '00000326' AS col3, NULL as col4 FROM DUAL
	UNION 
	SELECT NULL AS col1, NULL AS col2, NULL AS col3, 'ZZZ0' as col4 FROM DUAL
	UNION 
	SELECT NULL AS col1, NULL AS col2, '00090521' AS col3, NULL as col4 FROM DUAL
	)

SELECT 
	COALESCE(
		CASE 
			WHEN cou.col1 IS NOT NULL AND cou.col2 IS NOT NULL THEN cou.col1 || '-' ||  cou.col2
			ELSE COALESCE(cou.col1,cou.col2)
		END,cou.col3, cou.col4) AS response1
	,COALESCE(cou.col1 || '-' ||  cou.col2, cou.col3, cou.col4) AS response2
	
FROM cou
;

SQL> WITH cou AS (
  2     SELECT 'Jean' AS col1, 'Claude' AS col2, NULL AS col3, NULL as col4 FROM DUAL
  3     UNION
  4     SELECT 'Laurent' AS col1, NULL AS col2, NULL AS col3, NULL as col4 FROM DUAL
  5     UNION
  6     SELECT NULL AS col1, 'Sylvain' AS col2, NULL AS col3, NULL as col4 FROM DUAL
  7     UNION
  8     SELECT NULL AS col1, NULL AS col2, '00000326' AS col3, NULL as col4 FROM DUAL
  9     UNION
 10     SELECT NULL AS col1, NULL AS col2, NULL AS col3, 'ZZZ0' as col4 FROM DUAL
 11     UNION
 12     SELECT NULL AS col1, NULL AS col2, '00090521' AS col3, NULL as col4 FROM DUAL
 13     )
 14  SELECT NVL2(col1||col2, TRIM('-' FROM col1||'-'||col2), COALESCE(col3, col4))
 15  FROM cou
 16  /
NVL2(COL1||COL2
---------------
Jean-Claude
Laurent
Sylvain
00000326
00090521
ZZZ0

SQL> WITH cou AS (
  2     SELECT 'Jean' AS col1, 'Claude' AS col2, NULL AS col3, NULL as col4 FROM DUAL
  3     UNION
  4     SELECT 'Laurent' AS col1, NULL AS col2, NULL AS col3, NULL as col4 FROM DUAL
  5     UNION
  6     SELECT NULL AS col1, 'Sylvain' AS col2, NULL AS col3, NULL as col4 FROM DUAL
  7     UNION
  8     SELECT NULL AS col1, NULL AS col2, '00000326' AS col3, NULL as col4 FROM DUAL
  9     UNION
 10     SELECT NULL AS col1, NULL AS col2, NULL AS col3, 'ZZZ0' as col4 FROM DUAL
 11     UNION
 12     SELECT NULL AS col1, NULL AS col2, '00090521' AS col3, NULL as col4 FROM DUAL
 13     )
 14  SELECT CASE
 15           WHEN col1 IS NOT NULL AND col2 IS NOT NULL THEN col1||'-'||col2
 16           WHEN col1 IS NOT NULL                      THEN col1
 17           WHEN col2 IS NOT NULL                      THEN col2
 18           WHEN col3 IS NOT NULL                      THEN col3
 19           WHEN col4 IS NOT NULL                      THEN col4
 20           ELSE ''
 21         END
 22  FROM cou
 23  /
CASEWHENCOL1ISN
---------------
Jean-Claude
Laurent
Sylvain
00000326
00090521
ZZZ0