A PRIMARY KEY constraint in SQL Server is a field or column which ensures that each entry in a table is must be unique and not null.
A primary key can be created at the column or table level. The following is an example to illustrate this:

A PRIMARY KEY constraint in SQL Server is a field or column which ensures that each entry in a table is must be unique and not null.
A primary key can be created at the column or table level. The following is an example to illustrate this: