How to define Primary Key in POSTGRESQL

 Primary Key is a key how data physically aligned in the memory system. It will give ability for fast retrieval of data.

Key aspects in primary key

1. When you define a primary key PostgreSQL automatically creates a unique B-tree index on the columns available in the table.
2. Use SERIAL or BIGSERIAL for auto-incrementing primary keys. These types automatically generate unique sequential values. refer (available data types in POSTGRESQL)
3. Each table can have only one primary key
4. but a primary key can consist of multiple columns (composite key).

Example for creating table

CREATE TABLE Wings
         ( 
             WingID uuid primary key, 
             WingName VARCHAR(100), 
             IsActive boolean 
        );

Alter the existing table:

ALTER TABLE Wings ADD COLUMN ColID SERIAL PRIMARY KEY;