Oracle NULL-Related Functions

There are different type of null related function in oracle.

NVL function will check whether the first input parameter is null, if its null value,
 it returns the second parameter value.
The Oracle/PLSQL DECODE function has the functionality of an IF-THEN-ELSE statement.

* Oracle DECODE() function compares the first argument with the second argument.
IF they are equal, the function returns the third argument which is the string.
NVL2 function will check the first parameter, and return second parameter
if the first parameter is not null, otherwise returns third parameter.
COALESCE, returns the first not null expression in the given input parameters
NULLIF will compare the input parameters ( first and second parameter ), and returns
NULL of both are same, otherwise returns the first parameter value.