Need SQL Query

Hi SQL Experts,
Need help in getting below output :

create table sales_tab
(
sales_date date,
sales number
)
;

insert into sales_tab values('01-MAY-2013',101);
insert into sales_tab values('02-MAY-2013',102);
insert into sales_tab values('03-MAY-2013',103);
insert into sales_tab values('04-MAY-2013',104);
insert into sales_tab values('05-MAY-2013',105);
insert into sales_tab values('06-MAY-2013',106);
insert into sales_tab values('07-MAY-2013',107);
commit;


Need SQL query to get output like below.



SALES_DAT      SALES  SALES_DAT_prev   SALES_prev
--------- ------------------- ---------- ----------

07-MAY-13        107   06-MAY-13        106
06-MAY-13        106   05-MAY-13        105
05-MAY-13        105   04-MAY-13        104