Oracle function sample

CREATE OR REPLACE FUNCTION FN_GET_DD (
    vi_seq IN VARCHAR2
)
    RETURN VARCHAR2 IS reStr VARCHAR2(50);

BEGIN
    reStr := '';

    SELECT DD INTO reStr
    FROM DDDD
    WHERE DD = vi_seq;

    RETURN reStr;
    EXCEPTION
      WHEN NO_DATA_FOUND THEN
        RETURN '';
      WHEN OTHERS THEN
        RETURN '';

END    FN_GET_DD;
/