ORA-00907: 创建外键 Oracle 12c 时缺少右括号

我想制作一张包含一个自动生成的主键和两个外键的表，但我遇到了这个错误...

create table answers
( id number generated by default on null as identity primary key
, question_id number foreign key references questions(id)
, user_id number foreign key references users(id)
, answer varchar(1000)
, post_date date);

create table answers (id number generated by default on null as identity primary key, question_id number foreign key references questions(id), user_id number foreign key references users(id), answer varchar(1000), post_date date)

第 1 行错误： ORA-00907: 缺少右括号

然后，我尝试了这个：

create table answers
( id number generated by default on null as identity primary key
, question_id number foreign key (question_id) references questions(id)
, user_id number foreign key (user_id) references users(id)
, answer varchar(1000)
, post_date date );

create table answers
( id number generated by default on null as identity primary key
, question_id number foreign key (question_id) references questions(id)
, user_id number foreign key (user_id) references users(id)
, answer varchar(1000)
, post_date date )
                                                                                                     *

第 1 行错误： ORA-00907: 缺少右括号

它仍然给出同样的错误！

但是，如果我分两步进行：

create table answers
( id number generated by default on null as identity primary key
, question_id number not null
, user_id number not null
, answer varchar(1000)
, post_date date );

Table created.

alter table answers
add foreign key (question_id) references questions(id) add foreign key (user_id) references users(id);

表已更改。

谁能帮我摆脱这个困境吗？

当将约束内联定义为列定义的一部分时，您不需要说foreign key:

create table answers
( id number generated by default on null as identity primary key
, question_id number references questions(id)
, user_id number references users(id)
, answer varchar(1000)
, post_date date);

祝你好运。