In Oracle/PLSQL, the NVL function lets you substitute a value when a null value is encountered.

The syntax for the NVL function is:

• NVL( string1, replace_with_if_null ) string1 is the string to test for a null value. replace_with is the value returned if string1 is null.

Both parameters of the function have to be of the same data type. You cannot use this function to replace a null integer by a string unless you call the TO_CHAR function on that value:

• NVL(TO_CHAR(numeric_column), 'some string')