What is NVL function and how can use it?

NVL function  is used to substitute null values with another not null value.

The syntax for NVL function is:

NVL(original, ifnull)

If the value of  ‘original’  parameter is null, it returns the value of ‘ifnull’ parameter

 Example:

D:\app\Admin\virtual\virtual\product\12.2.0\dbhome_1\bin>sqlplus/nolog
 SQL*Plus: Release 12.2.0.1.0 Production on Fri Feb 25 16:17:57 2022
 Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 SQL> conn mereba/mereba@orcl
Connected

---When the 'original' value is null
SQL> select NVL(null, 'MerebaTech') as value from dual;
 VALUE
----------
MerebaTech

---When the 'original' value is not null
SQL> select NVL('Information', 'MerebaTech') as value from dual;
 VALUE
-----------
Information

--- When the 'original' is not null and the 'ifnull' is null
SQL> select NVL('Information', null) as value from dual;
 VALUE
-----------
Information