oracle - 与 ORA-01400 错误相关的奇怪行为

Question

我正在我们的数据库上创建一个带有版本的表Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64b

create table tahakkuk_kalem(
                           id       int generated always as identity primary key,       
                           aciklama varchar2(250),
                           tur      int default 0 not null 
                          );

然后应用一些插入语句：

SQL> insert into tahakkuk_kalem(aciklama) select 'Atıksu' from dual;

SQL> select * from tahakkuk_kalem;

ID  ACIKLAMA  TUR
--  --------  --- 
1   Atıksu     0

SQL> rollback;

SQL> insert into tahakkuk_kalem(aciklama,tur) select 'Atıksu',0 from dual;

ID  ACIKLAMA  TUR
--  --------  --- 
2   Atıksu     0

SQL> rollback;

到目前为止一切顺利，但如果我发表以下声明；

SQL> insert into tahakkuk_kalem(aciklama,tur) 
     select 'Atıksu',0 from dual union all select 'Ceza',0 from dual;

遇到了一个难以理解的错误声明：

ORA-01400:无法将 NULL 插入 ("MY_SCHEMA"."TAHAKKUK_KALEM"."ID")

你有什么意见可能是什么原因？