创建数据库外键约束搞不会了

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'primary key ,
longzhengcheng_id int(10),
gname varchar(30) not null,
num int(3)' at line 2

应该是主键的语法错了吧,贴一下完整的sql语句?