A primary key in SQL Table helps to identify each row/record in a table uniquely.
Here is the characteristic of Primary Key in SQL Table
ColumnName datatype not null identity(1,1) PRIMARY KEY, Note: identity(1,1) seed not Necessary while creating the primary key, but in general we set the identity seed for Primary Key column most of the time.
CREATE TABLE ClassStudentMap ( CSId int not null identity(1,1) PRIMARY KEY, ClassId int NOT NULL, StudentId bigint NOT NULL );
You may check the Foreign Key to understand the more insight about Primary Key.