If you want to create a GUID then SYS_GUID()
is what you should be using, you can create this in a table as per the linked question. It's unclear from the documentation whether SYS_GUID()
is incrementing. It might be but that's not really a statement that imparts trust.
The next part of your question (and some comments) keeps asking about clustered primary keys. This concept does not exist in the same way in Oracle as it does in SQL Server and Sybase. Oracle does have indexed organized tables (IOT) ...
... a table stored in a variation of a B-tree index structure... rows are stored in an index defined on the primary key for the table. Each index entry in the B-tree also stores the non-key column values. Thus, the index is the data, and the data is the index.
There are plenty of uses for IOTs but it's worth bearing in mind you're altering the physical structure of the database on the disk for "performance reasons". You're doing the ultimate of all premature optimizations using something that has both negative and positive aspects. Read the documentation and be sure that this is what you want to do.
I would generally use an IOT only when you don't care about DML performance but when you do a lot of range scans, or you need to order by the primary key. You create an IOT in the same way as you would an ordinary table, but because everything you want is now part of the table everything goes in your table definition:
create table test_table (
id raw(32) default sys_guid()
, a_col varchar2(50)
, constraint pk_my_iot primary key (id)
) organization index;
It's worth noting that even with an IOT you must use an explicit ORDER BY in order to guarantee returned order. However, because of the way this is stored Oracle can table a few short cuts:
select *
from ( select *
from test_table
order by id )
where rownum < 2
As with everything, test, don't assume that this is the structure you want.