Object Types are available since Oracle 8i, but just recently I encountered a situation were they seemed to be usefull. Picture this: We have a product that has a certain size (length, width and heigth) of its own and a certain size when packed into a box. Ofcourse we could model this by repeating the length-, width- and heigth-attributes for the two sizes, but (mostly) the same checks are liable for both sizes. And this 'size' is also used in other tables. So my idea was : defining an Object Type could be usefull here! So here we start, first create the Object Type "cbm_type": SQL>create or replace 2 type cbm_type as object 3 ( length number(6,2) 4 , width number(6,2) 5 , heigth number(6,2) 6 ) 7 / Type created. Now create the table (I defined cbm as not null, because the length, width and height should always be known): SQL>create table product 2 ( 3 description varchar2(30) not null, 4 cbm cbm_type not null 5 ) 6 / Table created. Now add some data: SQL>ins