SELECT DEPT_NO,DEPT_NAME FROM DEPT D WHERE EXISTS ( SELECT ‘X' FROM EMP E WHERE E.DEPT_NO = D.DEPT_NO);
Type of Condition EXISTSOperation TRUE if a subquery returns at least one row. ExampleSELECT department_id FROM departments d WHERE EXISTS (SELECT * FROM employees e WHERE d.department_id = e.department_id);
FROM EMP E WHERE E.DEPT_NO = D.DEPT_NO);
EXISTSOperation
TRUE if a subquery returns at least one row. ExampleSELECT department_id
FROM departments d
WHERE EXISTS
(SELECT * FROM employees e
WHERE d.department_id
= e.department_id);
exists(这里的数据较多)