-- 1. 조인 후 중복제거 SELECT DISTINCT a.aid, a.name FROM a , b WHERE a.aid = b.aid AND b.name = '검색어' ; -- 2. 중복제거 후 조인 SELECT a.aid, a.name FROM a , (SELECT DISTINCT b.aid FROM b WHERE b.name = '검색어' ) b WHERE a.aid = b.aid ; -- 3. IN 서브쿼리 SELECT a.aid, a.name FROM a WHERE a.aid IN (SELECT b.aid FROM b WHERE b.name = '검색어' ) ; -- 4. EXISTS 서브쿼리 SELECT a.aid, a.name FROM a WHERE EXISTS (SELECT 1 FROM b WHERE b.name = '검색어' AND b.aid = a.aid ) ;