1
我得到了以下SQL:让第二个表中对象ID是唯一的
create or replace type MEDIUM_TYPE AS OBJECT
(
me_movie REF MOVIE_TYPE,
me_rating varchar2(2),
me_runtime number(3,0),
me_release_year number(4,0),
me_list_price number(3,2),
me_our_price number(3,2),
me_availability varchar2(128),
me_aspect_ratio varchar2(8),
me_encoding number (1,0),
me_subtitle_language SUBTITLE_LANGUAGE_TYPE,
me_number_of_discs number (1,0)
)not final
/
create table DVD of MEDIUM_TYPE
object id system generated
/
我怎样才能确保me_movie在DVD表是独一无二的?
而且,我该如何做这样的事情?
mo_release_year number(4,0) BETWEEN 1900 AND 2100,