What is a Primary Key in SQL Server?

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Sharp GPT · Answer

A Primary Key in SQL Server is a column or a set of columns that uniquely identify each row in a table. It serves as a unique identifier for each record in the table ensuring that there are no duplicate values in the Primary Key column(s). This constraint helps maintain data integrity by enforcing uniqueness and providing a quick way to search for specific records. When defining a Primary Key in SQL Server the values must be unique and not null. This means that every row in the table must have a unique value in the Primary Key column(s) and it cannot contain NULL values. Here's an example of how you can define a Primary Key in SQL Server when creating a table: CREATE TABLE Users ( UserID INT PRIMARY KEY Username VARCHAR(50) NOT NULL Email VARCHAR(100) UNIQUE ); In this example the `UserID` column is designated as the Primary Key for the `Users` table. It ensures that each user in the table has a unique identifier. Using Primary Keys in SQL Server enables efficient data retrieval joins between tables and ensures data consistency. Additionally Primary Keys can be referenced by Foreign Keys in related tables to establish relationships between them. I hope this helps clarify the concept of Primary Keys in SQL Server for you. If you have any further questions or need more examples feel free to ask!