User Defined Function

Purpose

The User Defined Function masking format lets you define your own logic to mask column data. The return value of the user-defined function is used to replace the original values. The user-defined function is a PL/SQL function that can be invoked in a SELECT statement.

Inputs

• Package Name: The name of the database package
• Function Name: The name of the database function

The database function has a fixed signature:

function udf_func (rowid varchar2, column_name varchar2, original_value varchar2) return varchar2;

where:

• rowid is the row identifier of the row containing the value to be masked.
• column_name is the name of the column to be masked.
• original_value is the column value to be masked.

Supported Data Types

• Character
• Numeric
• Date

Characteristics

• Supports Double-Byte Characters: Yes
• Combinable: Yes
• Deterministic: Yes, depending on the function defined
• Reversible: No
• Uniqueness: Yes, depending on the function defined

Example

Suppose you create a user-defined function to mask string values.

To create the user-defined function, you might use the following code to randomize the string values. This example is simple, however you can write more complex code to suit your business use case.

CREATE OR REPLACE FUNCTION 
change_value (rowid varchar2, column_name varchar2, mask_value varchar2) 
RETURN varchar2
IS
BEGIN
    RETURN DBMS_RANDOM.STRING('A',8);
END;