The Oracle AND PL/SQL NVL function replace null with a value.
If expr1 is null, then NVL returns expr2, if expr1 is not null, then NVL returns expr1.
The general format is:
NVL(expr1, expr2)
Example 1:
SELECT NVL(STATUS,0) FROM INVOICE;
returns:
3
1
0
0
2
Example 2:
SELECT NVL(NULL,'none') FROM DUAL;
returns:
none