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Create Primary key constraint in SQL Server Database


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

  • Primary keys must contain unique values
  • primary key column cannot have NULL values
  • Table can have only one primary key (can be composite with multiple fields)

How to create Primary key in SQL

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.

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PRIMARY KEY Constraint in SQL Database