SELECT 사람, KEY FROM TAB
WHERE 사람 = 'A'
AND KEY NOT IN (SELECT KEY FROM TAB WHERE 사람='B') ;

------------------------------------------------------

SELECT 사람, KEY FROM TAB
WHERE 사람 = 'A'
AND KEY IN ( SELECT KEY FROM TAB GROUP BY KEY HAVING 1 = COUNT(*) );

--------------------------------------------------------------------

SELECT 사람, KEY FROM TAB
WHERE 사람 ='A'
AND KEY IN ( 
SELECT KEY FROM TAB WHERE 사람 ='A' MINUS 
SELECT KEY FROM TAB WHERE 사람 ='B'
);

등등등....?

WITH t AS
(
SELECT 'A' id, 3 cd FROM dual
UNION ALL SELECT 'A', 5 FROM dual
UNION ALL SELECT 'B', 2 FROM dual
UNION ALL SELECT 'B', 3 FROM dual
UNION ALL SELECT 'B', 6 FROM dual
)
SELECT cd
  FROM t
 GROUP BY cd
 HAVING COUNT(*) = COUNT(DECODE(id, 'A', 1))
;

감사합니다 ^^

DECODE로 해결했어요~

A와 B라는 사람의 키칷은 따로 없어서 ㅠ_ㅠ 데이터 뽑아 내기가 넘 힘들었어요 ㅠㅠ

중복을 제거하는 방법이 이렇게나 많았군요~!! ^^

알려주셔서 감사합니다~!!