Auto rotation table in oracle

Question

Hi,
Is there any strcuture or fucntion that can make the table have something like rotation.
I mean the record can be first in first delete.
So,for example , even the table have limit row for example , 100 row .
so, the new data can be replace the oldest row in the table auto and insert into the table .
so the new row will replace the oldest 99 th row auto .the table still keep 100 row but the data can be update .
Is it "partition" or other ??
how can I create it .
Please give me in detailed

Answer 1

when creating sequences there is a cycle option so in your scenario after 100 it would go to one.
you could take advantage of that in a stored procedure or better yet a trigger
(allthough it would probably need to be a three trigger approach because reading from the table you are going to update insert
will probably lead to a mutating trigger exception)
here it is with the stored procedure although the trigger would probably be
better because if two separate sessions run the procedure you might end up with duplicate rows in your tables.
you could of course put a unique constraint there to throw an error when that happens.
anyway. here it is with maximum rows of 5
create sequence test_seq
increment by 1
start with 1
maxvalue 5
cycle
nocache;
create table rotating_table as
select 1 id, 'A' txt from dual
where 1 = 2;
create or replace procedure insert_into_rotating_table (v_txt  rotating_table.txt%type)  as
aSequence number;
begin
   select test_seq.nextval into aSequence from dual;
   delete from rotating_table where id = aSequence;
   insert into rotating_table values (aSequence, v_txt);
end;
exec insert_into_rotating_table('A');
exec insert_into_rotating_table('B');
exec insert_into_rotating_table('C');
exec insert_into_rotating_table('D');
exec insert_into_rotating_table('E');
exec insert_into_rotating_table('F');
exec insert_into_rotating_table('G');
select * from rotating_table;
ID     TXT
3     C
4     D
5     E
1     F
2     G