Let’s take a closer look at defining Auto Increment Primary Key in pgAdmin.

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What is pgAdmin Auto Increment?

pgAdmin is the leading Postgres Open Source management tool. It is very important to include a primary key in every table for a relational database like PostgreSQL. Therefore, we have to make sure that there is a crucial primary key column in every table. Postgres basically offers two ways to do this.

1. With a Serial datatype
2. With a Custom Sequence

Defining pgAdmin Auto Increment Primary Key With Serial Datatype

Smallserial, serial, and bigserial are data types in Postgres. These are not true types but are similar to the AUTO INCREMENT property that some other databases support.

If we want a serial column to have a unique constraint or to be a primary key, we must now specify it like other data types. The Serial type generates integer columns. Bigserial generates a bigint column and Smallserial creates a smallint column. The syntax is as follows:

CREATE TABLE tablename (
   colname SERIAL
);

Now we can consider an example to understand pgAdmin auto-increment.

1. Firstly create a table with table name: STUDENT

   testdb=# CREATE TABLE STUDENT(
      ID  SERIAL PRIMARY KEY,
      SNAME           TEXT      NOT NULL,
      TEACHER         TEXT      NOT NULL,
      MARK            INT       NOT NULL
   );
2. Now insert values to the table.

   INSERT INTO STUDENT (SNAME,TEACHER,MARK)
   VALUES ( 'Science', 'Lisa', 50 );

Repeat this 3 times. This will result in 3 tuples in the table Subject. The records will be:

id | sname      | Teacher  | Mark     
----+----------+----------+----------
  1 | Science  |  Lisa    | 50 
  2 | Maths    |  Jiz     | 45     
  3 | English  |  Mark    | 49

Defining pgAdmin Auto Increment Primary Key With Custom Sequence

There is also another way to define the Auto Increment Primary Key in PostgreSQL. Sometimes the standard incremental nature of SERIAL and BIGSERIAL data types may not suit the needs. So we need to perform the same auto incremented primary key functionality for the column by creating a custom SEQUENCE.

Let’s examine an example to understand it better.

CREATE SEQUENCE books_sequence
  start 2
  increment 2;

The next value of our sequence needs to be evaluated with nextval(‘books_sequence’). Then we can use it as an id when we INSERT a new record into the books table.
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INSERT INTO books
  (id, title, primary_author)
VALUES
  (nextval('books_sequence'), 'The Hobbit', 'Tolkien');

In this example, the primary key will increment by two starting at 100 for every insert of a new tuple. Hence we can customize the auto increment option according to our needs.

We can also use minvalue and maxvalue options to indicate extreme values. The CYCLE option allows the sequence to “loop around” once it reaches the maxvalue, returning to the start value and beginning the climb all over again

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Conclusion

For Postgres, it is crucial to add a primary key column to every table. Here our Support team shows two methods to accomplish this task of pgAdmin Auto Increment.