create sequence seq_字段名_表名

minvalue 1

maxvalue 999999999999999999999999999

start with 1

increment by 1

cache 10;

CREATE OR REPLACE TRIGGER tri_字段名_表名

BEFORE insert ON 表名

FOR EACH ROW

begin

    select seq_字段名_表名.Nextval into:New.自增字段名 from dual;

end;