ORACLE 12C 12項強化功能之一 建TABLE 時可以直接用Sequence

oracle 12c database new features Oracle 12項 資料庫新特性 
Default value of column can use a sequence.nextval
在以往ORACLE 9i ,10g,11g  建sequence 都要建一個Trigger 將Seqence  作改變 

參考Create table with default sequence
 Creating a Table with a DEFAULT ON NULL Column Value: Example 

The following statement creates a table myemp, which can be used to store employee data. The department_id column is defined with a DEFAULT ON NULLcolumn value of 50. Therefore, if a subsequent INSERT statement attempts to assign a NULL value to department_id, then the value of 50 will be assigned instead.

CREATE TABLE myemp (employee_id number, last_name varchar2(25),
                    department_id NUMBER DEFAULT ON NULL 50 NOT NULL);

以上官網的範例 
以下我作個實際範例 

create table example (
production varchar2(100),
productioserial number default on null 1 not null);



insert into example(production) values('item2');
commit;

insert into example(production) values('item2');
commit;

select * from example;

Results ：  看樣子是會帶DEFAULT 值出 ，可是這不是我要的自動增加 
PRODUCTION  PRODUCTIOSERIAL
----------------------------------------------------------------
item1     1 
item2     1

CREATE TABLE example2 (productname varchar2(100),serial NUMBER GENERATED BY DEFAULT AS IDENTITY (START WITH 1 INCREMENT BY 1));

insert into example2(productname) values ('itema');

 insert into example2(productname) values ('itemb');

PRODUCTNAME               SERIAL

--------------------------------

itema                          1 

itemb                          2