求大神指导，插入数据的一个sql语句错误

在行 1 上开始执行命令时出错:
declare
cursor emp_cursor is
select e.jnumber from employee e left join Labour_User L on e.jnumber=L.jnumber where L.jnumber is null;
begin
for r in emp_cursor loop
insert into Labour_User(JNUMBER,PASSWORD,ROLETYPE)values(r.jnumber,r.jnumber,'普通教职工');
end loop;
end;
错误报告:
ORA-01400: cannot insert NULL into ("LABOURUNIOn"."LABOUR_USER"."ID")
ORA-06512: at line 6
01400. 00000 - "cannot insert NULL into (%s)"

提示很明显，Labour_User表的ID是不为空但是插入语句没有给值

insert into Labour_User(ID,JNUMBER,PASSWORD,ROLETYPE)
values(<ID>,r.jnumber,r.jnumber,'普通教职工');