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c# and SQL interview question Video :- What is the difference between unique key and primary key?

  • Unique key can have nulls .Primary key cannot have nulls.
  • In a single table we can create multiple unique keys.In a single table we can have only one primary key.
  • Unqiue key creates a non-clustered index by default.Primary Key created a clustered index by default.
  • Both unique keys and primary keys can be referenced by foreign key.


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Shivprasad koirala Koirala
I am a Microsoft MVP for ASP/ASP.NET and currently a CEO of a small E-learning company in India. We are very much active in making training videos , writing books and corporate trainings. Do visit my site for .NET, C# , design pattern , WCF , Silverlight , LINQ , ASP.NET , ADO.NET , Sharepoint , UML , SQL Server training and Interview questions and answers
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