Oracle 06. DML ( Data Manipulation Language )

(1) 설명 
     1) 테이블내의 데이터를 '입력', '수정', '삭제'하는 SQL문 

 

(2) 종류 
     1) insert
          ex) insert into DEPT2 values(50, '개발', '서울');

          Err) insert into EMP2 values(8000, '홍길동', '개발자', 7839, SYSDATE, 8000, null, 60); --에러(FK)
          ex> insert into EMP2 values(8000, '홍길동', '개발자', 7839, SYSDATE, 8000, null, 50);

          Err) insert into EMP2(EMPNO, ENAME, SAL, HIREDATE) values(8000, '이순신', 7000, SYSDATE); --에러(PK)
          ex) insert into EMP2(EMPNO, ENAME, SAL, HIREDATE) values(9000, '이순신', 7000, SYSDATE);

          Err) insert into EMP2(ENAME, SAL, HIREDATE) values('강감찬', 6000, SYSDATE); --에러(PK)
          ex) insert into EMP2(EMPNO, SAL, HIREDATE) values(9999, 6000, SYSDATE);

          확인) select * from EMP2 where EMPNO>=8000;

     2) update 
          ex) update EMP2 set ENAME='홍길순', SAL=8500 where EMPNO=8000;
          ex) update EMP2 set EMPNO=8001 where EMPNO=8000; --PK컬럼도 가능 
          ex) update EMP2 set DEPTNO=10 where EMPNO=8001; --FK컬럼도 가능

     3) delete  
          ex) delete from EMP2 where EMPNO=9999;
          ex) delete from DEPT2 where DEPTNO=30;
          1) on delete cascade 옵션으로 FK제약조건이 부여되었다면 자식데이터존재유무와 상관없이 삭제 됨
         
          cf) cascade 를 이용한 부모 테이블 삭제 
               ex) drop table DEPT2 cascade constraint;