postgresql设置主键自增

法一：

CREATE TABLE banners  
(  
  id SERIAL primary key ,  
  name character varying,  
)  

 法二：

CREATE SEQUENCE banners_id_seq  
START WITH 1  
INCREMENT BY 1  
NO MINVALUE  
NO MAXVALUE  
CACHE 1;  
  
alter table banners alter column id setdefault nextval('banners_id_seq');