SALARIO     COMISION   SALARIO+NVL(COMISION,0)
----------             ----------                  -----------------------
  1040                 1040
  1500                   390                                 1890
  1625                   650                                 2275
  2900                 2900
  1600                 1020                                 2620
  3005                 3005
  2885                 2885
  3000                 3000
  4100                 4100
  1350                        0                                 1350
  1430                 1430
  1335                 1335
  3000                 3000
  1690                 1690

14 filas seleccionadas.

En este otro ejemplo, al aplicar a la comisión la función NVL en la columna SALARIO +  OMISION, no resultan valores nulos.

POWER(m, exponente). Prueba con números positivos y negativos:

SQL> SELECT POWER(2,4), POWER(2,-4), POWER(3.5, 2.4), POWER(4.5, 2) FROM DUAL;

POWER(2,4)   POWER(2,-4)         POWER(3.5,2.4)       POWER(4.5,2)
    ----------             -----------                     --------------                  ------------
         16                    ,0625                       20,2191692                  20,25

ROUND(número [,m]). Prueba con redondeo positivo:

SQL> SELECT ROUND(1.56,1), ROUND(1.56), ROUND(1.2234,2), ROUND(1.2676, 3) FROM DUAL;

ROUND(1.56,1)      ROUND(1.56)      ROUND(1.2234,2)     ROUND(1.2676,3)
-------------                       -----------                   ---------------                 ---------------
     1,6                                   2                              1,22                             1,268

Prueba con redondeo negativo:

SQL> SELECT ROUND(145.5, -1), ROUND(145.5, -2), ROUND(145.5, -3), ROUND(141,-1), ROUND(145,-1) FROM DUAL;

ROUND(145.5,-1)      ROUND(145.5,-2)        ROUND(145.5,-3)          ROUND(141,-1)        ROUND(145,-1)
  ---------------                      ---------------                     ---------------                      -------------                        -----------
         150                                  100                                     0                                       140                                 150