avoid divide by zero error with nullif

[oracle@stormking cdb12102 SQL]$ cat div0.SQL
SELECT n, 1 / NULLIF ( n, 0 ) rn
FROM
(
        SELECT level - 3 n
        FROM dual
        CONNECT BY level <= 5
)
ORDER BY n
;

quit
[oracle@stormking cdb12102 SQL]$ sqlplus u/u@//stormking:1521/pdbm @ div0.SQL

SQL*Plus: Release 12.1.0.2.0 Production ON Sat Oct 24 00:17:44 2015

Copyright (c) 1982, 2014, Oracle.  ALL rights reserved.

LAST Successful login TIME: Sat Oct 24 2015 00:17:39 -04:00

Connected TO:
Oracle DATABASE 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
WITH the Partitioning, Automatic Storage Management, OLAP, Advanced Analytics
AND REAL Application Testing options


         N         RN
---------- ----------
        -2        -.5
        -1         -1
         0
         1          1
         2         .5