Thanks for your response John.
Any other way? A database upgrade just for this requirement is not quite feasible.
If you cannot upgrade then you have two choices.
Declare a default value for the column and make sure that whenever you insert into the the table that the defaulted column is not in the column list if you do not have a specific value to insert.
Create a trigger on the table and set the column value to the default value if, and only if, it is null.
>> Any other way?
alter table <table> modify ( <column> default 'some value' );
Suppose there is a table with 3 columns and for 3rd column, I want to have a default value clause such that wenever NULL value comes, it should insert the default value.
That isnt' what DEFAULT values are for. They are used to insert a value when you do NOT provide a value in the INSERT statement. If you provide a value or NULL Oracle will insert that and NOT use any default specified unless you define the column as NOT NULL in which case you will get an exception if you try to provide null.
Just add a simple trigger on the table to check that column for null and provide the value you want used if the column would otherwise be null.