What is a Primary Key in SQL Server?

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C# Corner Support · Answer

Certainly! In the context of SQL Server within the realm of .NET technology a Primary Key is a crucial concept in database design. A Primary Key constraint is used to uniquely identify each record in a table. Here are some key points about Primary Keys in SQL Server: 1. Uniqueness : A Primary Key column must contain unique values for each record. This uniqueness ensures that each row in a table can be uniquely identified. 2. NULL values : A Primary Key column cannot contain NULL values. Each record must have a value in the Primary Key column. 3. Indexing : By default defining a Primary Key in SQL Server creates a clustered index on that column. This helps in faster data retrieval and sorting. 4. Declaration in SQL : In SQL Server you can define a Primary Key using the `PRIMARY KEY` constraint during table creation or alter table statements. Example of creating a table with a Primary Key in SQL Server: CREATE TABLE Users ( UserID INT PRIMARY KEY UserName NVARCHAR(50) ); In this example `UserID` is the Primary Key for the `Users` table. It uniquely identifies each user in the table. In a .NET application interacting with SQL Server databases often involves working with tables that have Primary Keys to maintain data integrity and enable efficient querying. When designing databases for .NET applications understanding Primary Keys and their role in ensuring data uniqueness is essential for a robust and scalable system. If you have any specific questions or need further clarification on Primary Keys in SQL Server within the context of .NET technology feel free to ask!