Function to get the employee grade by passing person id and effective date

CREATE OR REPLACE FUNCTION getgrade (pid IN NUMBER, effdate IN DATE) RETURN VARCHAR2 IS

m_grade VARCHAR2(10);

BEGIN

    SELECT pg.NAME
      INTO m_grade
      FROM per_grades pg, per_all_assignments_f ppf
     WHERE ppf.GRADE_ID = pg.GRADE_ID
       AND ppf.person_id = pid
       AND TRUNC(effdate) BETWEEN TRUNC(ppf.EFFECTIVE_START_

DATE) AND TRUNC(ppf.EFFECTIVE_END_DATE);
--       AND ppf.ROWID IN (SELECT MAX(ROWID) FROM per_all_assignments_f GROUP BY person_id);
      
    RETURN m_grade;
   
EXCEPTION
    WHEN others THEN
         RETURN NULL;          

END;
/