Comparison Operators (P2-23)
- IN(list)
- SQL> conn scott/tiger
Connected.
SQL> SELECT dname
2 FROM dept
3 WHERE deptno IN(10,20);- DNAME
--------------
ACCOUNTING
RESEARCH
- WHERE deptno IN(10,20) == WHERE deptno=10 or deptno=20
- SQL> SELECT dname
2 FROM dept
3 WHERE deptno=10 or deptno=20; - DNAME
--------------
ACCOUNTING
RESEARCH
- WHERE deptno IN(10,20) == WHERE deptno=10 or deptno=20 == SELECT dname FROM dept WHERE deptno=ANY(10,20)
- SQL> SELECT dname
2 FROM dept
3 WHERE deptno=ANY(10,20) - DNAME
--------------
ACCOUNTING
RESEARCH
- LIKE
Wildcard '%'는 0개 이상의 문자를 대표한다.
Wildcard '_'는 1개의 문자를 대표한다.
- // 'A'로 시작하는 부서이름 검색
- SQL> SELECT dname
2 FROM dept
3 WHERE dname like 'A%'; - DNAME
--------------
ACCOUNTING
- IS NULL
null값은 비교연산자('=') 사용 불가
'IS NULL' 이용해야함.
- // 잘못된 코드
- SQL> SELECT ename
2 FROM emp
3 WHERE comm = null; - no rows selected
- // 정상코드
- SQL> SELECT ename
2 FROM emp
3 WHERE comm IS NULL; - ENAME
----------
SMITH
JONES
BLAKE
CLARK
SCOTT
KING
ADAMS
JAMES
FORD
MILLER - 10 rows selected.
ORDER BY Clause (P2-30)
ORDER BY 절은 가장 마지막에 써야함
정렬순서(ASC, DESC) 생략시 ASC(오름차순)이 기본값
- SQL> SELECT dname
2 FROM dept
3 ORDER BY dname; - DNAME
--------------
ACCOUNTING
OPERATIONS
RESEARCH
SALES
Oracle sorts nulls following all others in ascending order and preceding all others in descending order.
(null 값이 젤 나중~)
- SQL> SELECT ename, comm
2 FROM emp
3 ORDER BY comm; - ENAME COMM
---------- ----------
TURNER 0
ALLEN 300
WARD 500
MARTIN 1400
SMITH
JONES
JAMES
MILLER
FORD
ADAMS
BLAKE - CLARK
SCOTT
KING - 14 rows selected.
이 글은 스프링노트에서 작성되었습니다.