PostgreSQL 10 IDENTITY Column is an excellent feature of this version. Since the beginning of Microsoft SQL Server, IDENTITY Column is available with it.

SQL Server 2012 introduced Sequence Object, and since beginning SERIAL/BIGSERIAL (Sequence Object) are available in PostgreSQL.

The new IDENTITY Type Column is used to generate an automatic number.
Now, we have this great feature, and creating an auto-increment column is also very simple.

Why is IDENTITY good over SERIAL/BIGSERIAL (Sequence Object)?

Sequence Object requires additional permission
Managing the Sequence Object is difficult while migrating table structure

Check the below example:

Create a sample table with IDENTITY column:

CREATE TABLE tbl_test (
    id int GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
    name character varying
);

Insert few records:

INSERT INTO tbl_test (name) 
VALUES ('abc'), ('xyz'), ('pqr');

Check the result:

SELECT *FROM tbl_test;

id    |    name 
-------------------
1      |     abc
2      |     xyz
3      |     pqr

In this post, I am creating an auto increment PRIMARY KEY using a custom sequence of the PostgreSQL.

PostgreSQL already provides two data types for auto increment id, serial (4 bytes) & bigserial (8 bytes).
When we apply serial or bigserial to the particular column, internally it creates a default sequence object for that column and automatically it generates auto increment value for that column.

We can also create custom sequence object in the PostgreSQL and it also requires in some situation where we do not want to use default sequence value.

First, Create a sequence object:Starting with 100 and increment by 10

CREATE SEQUENCE seq_MyCustom_Id
    START 100
    INCREMENT 10
    NO MAXVALUE
    CACHE 1;

Create sample table:

CREATE TABLE tbl_SampleID
(
	ID INTEGER PRIMARY KEY
	,Name CHARACTER VARYING(50)
);

Use this sequence object and Insert sample data:

INSERT INTO tbl_SampleID
VALUES
(NEXTVAL('seq_MyCustom_Id'),'Anvesh')
,(NEXTVAL('seq_MyCustom_Id'),'Roy')
,(NEXTVAL('seq_MyCustom_Id'),'Martin');