코드만 체크하면 되나요?
혹시 코드는 같은데 이름은 다른 경우가 있어서 이름까지 체크해야 하는지?

WITH
T1 AS (
 SELECT * FROM (
 SELECT '' AS COLUMN_1,'' AS COLUMN_2 FROM DUAL
 UNION ALL SELECT '1001', '수박' FROM DUAL
 UNION ALL SELECT '1002', '고구마' FROM DUAL
 UNION ALL SELECT '1003', '오이' FROM DUAL
 UNION ALL SELECT '1004', '당근' FROM DUAL
 )
WHERE COLUMN_1 IS NOT NULL
)

,T2 AS (
 SELECT * FROM (
 SELECT '' AS COLUMN_1,'' AS COLUMN_2 FROM DUAL
 UNION ALL SELECT '1001', '수박' FROM DUAL
 UNION ALL SELECT '1002', '고구마' FROM DUAL
 )
WHERE COLUMN_1 IS NOT NULL
)

SELECT
		COLUMN_1
		,COLUMN_2
FROM
		(
		SELECT
				T1.COLUMN_1
				,T1.COLUMN_2
				,T2.COLUMN_2 AS EXISTS_YN
		FROM T1
		LEFT JOIN T2 ON T2.COLUMN_1 = T1.COLUMN_1
		)
WHERE EXISTS_YN IS NULL;


WITH
T1 AS (
 SELECT * FROM (
 SELECT '' AS COLUMN_1,'' AS COLUMN_2 FROM DUAL
 UNION ALL SELECT '1001', '수박' FROM DUAL
 UNION ALL SELECT '1002', '고구마' FROM DUAL
 UNION ALL SELECT '1003', '오이' FROM DUAL
 UNION ALL SELECT '1004', '당근' FROM DUAL
 )
WHERE COLUMN_1 IS NOT NULL
)

,T2 AS (
 SELECT * FROM (
 SELECT '' AS COLUMN_1,'' AS COLUMN_2 FROM DUAL
 UNION ALL SELECT '1001', '수박' FROM DUAL
 UNION ALL SELECT '1002', '고구마' FROM DUAL
 )
WHERE COLUMN_1 IS NOT NULL
)

SELECT
		*
FROM
		T1
WHERE
		NOT EXISTS(SELECT 'A' FROM T2 WHERE T2.COLUMN_1 = T1.COLUMN_1);