ORA-00907: 创建外键 Oracle 12c 时缺少右括号

Question

我想创建一个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 行的错误： 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 行的错误： ORA-00907: 缺少右括号

仍然报同样的错误！

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。

任何人都可以帮我解决这个问题吗？

Answer 1

将内联约束定义为列定义的一部分时，您无需说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。

Answer 2

您可以在底部定义外键，与列名不相邻，如下所示：

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