How to restric the duplicate value on nvarchar column in sql

Question

Hi How to restric the duplicate value on nvarchar column in sql Express 2008 Below is my table Hide Copy Code CREATE TABLE [dbo].[User]( [User_No] [int] IDENTITY(11) NOT NULL [User_Name] [nvarchar](max) NOT NULL ) ON [PRIMARY] GO I want to restric if the User_Name is duplicate.

Midhun T P · Answer

Hi You may have to change size of nvarchar. Please check below link - http://stackoverflow.com/questions/2863993/is-of-a-type-that-is-invalid-for-use-as-a-key-column-in-an-index

basit khan · Answer

Column 'User_Name' in table 'User' is of a type that is invalid for use as a key column in an index. User_Name is nvarchar column

Manas Mohapatra · Answer

You need to add Unique constraint to prevent duplicate records. http://stackoverflow.com/questions/1588984/how-to-make-no-duplicates-column-in-sql-server-2008

Midhun T P · Answer

Hi Try below query - ALTER TABLE [User] ADD CONSTRAINT UQ_Name UNIQUE (User_name)