Use function to check passwords : Function « Function Procedure Packages « Oracle PL/SQL Tutorial

SQL>
SQL> CREATE OR REPLACE FUNCTION myFunction(in_username IN VARCHAR,in_new_password IN VARCHAR,in_old_password IN VARCHAR)
  2  RETURN BOOLEAN
  3  AS
  4      pwd_okay BOOLEAN;
  5  BEGIN
  6      IF in_new_password = in_username THEN
  7         raise_application_error(-20001, 'Password may not be username');
  8      END IF;
  9      RETURN TRUE;
 10  END myFunction;
 11  /

Function created.

SQL>

27.1.Function
	27.1.1.	Functions
	27.1.2.	Describe a user-defined function
	27.1.3.	create or replace FUNCTION iifn(boolean_expression in BOOLEAN,true_number IN NUMBER,false_number IN NUMBER)
	27.1.4.	Storing PL/SQL function in the Database
	27.1.5.	Create a simple function
	27.1.6.	Creating a Function to deal with business rules
	27.1.7.	CREATE OR REPLACE a function
	27.1.8.	Calling a Function
	27.1.9.	Calling a Function for a table
	27.1.10.	Function without parameters
	27.1.11.	Exit a function
	27.1.12.	How to Call a Function from PL/SQL With or Without Parameters
	27.1.13.	Local Subprograms
	27.1.14.	Dependency Example
	27.1.15.	The FullName Function
	27.1.16.	PLW-05005: function NO_RETURN returns without value at line 21
	27.1.17.	Use function to check passwords