SELECT HIREDATE, TO_CHAR(HIREDATE, 'YYYY/MM/DD DAY') FROM EMP;
SELECT SYSDATE - 1 어제, SYSDATE 오늘, SySDATE +1 내일 FROM DUAL;
select ename, 19||substr(hiredate, 1,2) 년도, substr(hiredate, 4,2) 달
from emp
where substr(hiredate, 4,2) ='09';
SELECT DISTINCT DEPTNO FROM EMP;
SELECT * FROM emp WHERE SAL >= 3000 order by ename asc;
SELECT * FROM EMP WHERE COMM IS not NULL;
SELECT * FROM EMP WHERE ename NOT LIKE '%A%';