PostgreSQL中实现自增的三种方式举例

CREATE TABLE t_user (
    user_id integer GENERATED ALWAYS AS IDENTITY PRIMARY KEY ,
    user_name varchar(50) NOT NULL UNIQUE
)
INSERT INTO t_user (user_name) value ('tony')

-- SEQUENCE: public.t_user_user_id_seq

-- DROP SEQUENCE IF EXISTS public.t_user_user_id_seq;

CREATE SEQUENCE IF NOT EXISTS public.t_user_user_id_seq
    INCREMENT 1
    START 1
    MINVALUE 1
    MAXVALUE 2147483647
    CACHE 1;

ALTER SEQUENCE public.t_user_user_id_seq
    OWNER TO postgres;

CREATE SEQUENCE IF NOT EXISTS public.t_user_user_id_seq
    INCREMENT 1
    START 1
    MINVALUE 1
    MAXVALUE 2147483647
    CACHE 1
    NO CYCLE

CREATE TABLE t_user (
    user_id integer DEFAULT nextval('t_user_user_id_seq') PRIMARY KEY ,
    user_name varchar(50) NOT NULL UNIQUE
)

CREATE TABLE t_user (
    user_id serial PRIMARY KEY ,
    user_name varchar(50) NOT NULL UNIQUE
)

CREATE TABLE IF NOT EXISTS public.t_user
(
    user_id integer NOT NULL DEFAULT nextval('t_user_user_id_seq'::regclass),
    user_name character varying(50) COLLATE pg_catalog."default" NOT NULL,
    CONSTRAINT t_user_pkey PRIMARY KEY (user_id),
    CONSTRAINT t_user_user_name_key UNIQUE (user_name)
)

CREATE TABLE student
(
    id   int4 PRIMARY KEY,
    name VARCHAR
);

CREATE SEQUENCE student_id_seq START 1;

ALTER TABLE student
    ALTER COLUMN id SET DEFAULT nextval('student_id_seq'::regclass);