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
