关于oracle建表

有人能帮我看看我这个错在哪吗？
谢谢


```sql
SQL> create table student(
  2  Sno Varchar2(8) Primary key,
  3  Sname Varchar2(8) not null,
  4  Ssex NVarchar2(2) check(Ssex ='男' or Ssex='女'),
  5  Sbirthday date,
  6  Classno Varchar2(6) constraint Classno references class(Classno),
  7  Totalcredit Smallint default 0,
  8  Createdby Varchar2(8) default 21301147
  9  );
Ssex NVarchar2(2) check(Ssex ='男' or Ssex='女'),
                                              *
ERROR at line 4:
ORA-00907: missing right parenthesis


```我用的是oracle19c

报错很明显看,第四行,主键定义有问题,

create table student(
    Sno Varchar2(8) Primary key,
    Sname Varchar2(8) not null,
    Ssex NVarchar2(2) check(Ssex ='男' or Ssex='女'),
    Sbirthday date,
   Classno Varchar2(6) constraint Classno references class(Classno),
    Totalcredit Smallint default 0,
    Createdby Varchar2(8) default 21301147
    );

不是varchar2写成了nvarchar2报错么