EXISTS 조건식은 오른쪽에 지정되는 부질의를 실행한 결과가 하나 이상 존재하면 TRUE를 반환하고, 연산 실행 결과가 공집합이면 FALSE를 반환한다.
EXISTS expression
--selecting rows using EXISTS and subquery
SELECT 'raise' FROM db_root WHERE EXISTS(
SELECT * FROM condition_tbl WHERE salary < 2500000);
=== <Result of SELECT Command in Line 2> ===
'raise'
======================
'raise'
--selecting rows using NOT EXISTS and subquery
SELECT 'raise' FROM db_root WHERE NOT EXISTS(
SELECT * FROM condition_tbl WHERE salary < 2500000);
=== <Result of SELECT Command in Line 2> ===
There are no results.
0 rows selected.