Oracle中多个字段内容加密为MD5

CREATE OR REPLACE FUNCTION MD5(passwd IN VARCHAR2)RETURN VARCHAR2
IS
   retval varchar2(32);
BEGIN
    retval := (case when passwd is null then null else utl_raw.cast_to_raw(DBMS_OBFUSCATION_TOOLKIT.MD5(INPUT_STRING => passwd)) end);
    RETURN retval;
END;

使用案例：

select MD5('aaa'||'bbbb'||'ccc') from dual;