Selecting random records out of a table

Question

Hi,
I guess this question isn't new, but I didn't found anything about this using the search of this forum.
How can I get e.g. 5 random records out of a table?
I have a small table, which stores the special offers of a shop. Let us say, there are 30 records in it. How can I fetch (e.g.) 5 random records of this table?
I tried to use this statement in a loop:
SELECT t_item_id FROM tbl_special_offers SAMPLE (1) WHERE ROWNUM = 1
But this is a very small table, so most of the query returns no data. Additionally I have to check if this number was already selected and ignore it in this case. This isn't a good solution, is it?
Can somebody help me out with a better solution? Thanks :)

Answer 1

create or replace package shop_stuff
is
   function random_number return number;
end;
create or replace package body shop_stuff
is
   function random_number return number
   is
   begin
      return dbms_random.value;
   end;
begin
   dbms_random.initialize (to_number(to_char(sysdate,'mmddsssss')));
end;
create table tbl_special_offers (t_item_id number);
insert into tbl_special_offers values (1);
insert into tbl_special_offers values (2);
insert into tbl_special_offers values (3);
insert into tbl_special_offers values (4);
insert into tbl_special_offers values (5);
insert into tbl_special_offers values (6);
insert into tbl_special_offers values (7);
insert into tbl_special_offers values (8);
insert into tbl_special_offers values (9);
insert into tbl_special_offers values (10);
select t_item_id
  from (select t_item_id
          from tbl_special_offers
         order by shop_stuff.random_number)
where rownum <= 5                       
SQL> /
T_ITEM_ID
         6
         7
         5
         4
        10
SQL> /
T_ITEM_ID
         1
         5
         3
         9
         6
SQL> /
T_ITEM_ID
         6
         5
         3
         2
        10
SQL> /
T_ITEM_ID
        10
         2
         8
         4
         1
SQL>