1.添加一个Sequence，此处为ID_SEQUENCE。

2.添加对应表，并设置主键

3.设置触发器

create or replace trigger sys.id_add
before insert on SWACK.NUSER
for each row
-- WHEN (new.id is null)
-- local variables here
begin
select SWACK.ID_SEQUENCE.NEXTVAL into :new.id from dual;
end id_add;