how to Audit updates to table data using a table function that modifies SQL data

This function updates the salary of an employee specified by "updEmpNum", 4by the amount specified by "amount", and also records in an audit table named 4"audit_table", the user that invoked the routine, the name of the table 4that was modified, and the type of modification made by the user. A 4SELECT statement that references an UPDATE statement in the FROM clause is 4used to get back the updated row values.

CREATE FUNCTION update_salary(updEmpNum CHAR(4), amount INTEGER)
   RETURNS TABLE (emp_lastname VARCHAR(10),
                  emp_firstname VARCHAR(10),
                  newSalary INTEGER)
   LANGUAGE SQL
   MODIFIES SQL DATA
   NO EXTERNAL ACTION
   NOT DETERMINISTIC
   BEGIN ATOMIC
     INSERT INTO audit_table(user, table, action, time)
     VALUES (USER, 
             'EMPLOYEE',
             'Update of employee salary. Values: ' 
                || updEmpNum || ' ' || char(amount),
             CURRENT_TIMESTAMP);
     RETURN
       SELECT lastname, firstname, salary
         FROM FINAL TABLE(UPDATE employee 
                          SET salary = salary + amount
                          WHERE employee.empnum = updEmpNum);
   END