About DATABASE

SQL>SELECT empno, NVL  
        FROM  emp  
        WHERE deptno = 30;

         EMPNO  NVL(COMM,0)
       ----------     -----------
          7499              300
          7521              500
          7654             1400
          7698                0
          7844                0
          7900                0

Commsion이 없는 사원에 대해 0으로 바꾸어서 출력합니다. (comm, 0)

SQL> SELECT deptno,
                    DECODE(deptno, 10 , ’ACCOUNTING’ ,
                                             20 , ’RESEARCH’ ,
                                             30 , ’SALES’ ,
                                             40 , ’OPERATIONS’)
          FROM emp ;

     DEPTNO  DECODE(DEP
     ---------- ----------
        20        RESEARCH
        30        SALES
        30        SALES
        20        RESEARCH
        30        SALES
        30        SALES
        10        ACCOUNTING
        20        RESEARCH

부서가 10번이면 ’ACCOUNTING’를 20번이면 ’RESEARCH’를
30번이면 ’SALES’를 40번이면 ’OPERATIONS’를 출력하는 예제 입니다.