感谢大家的快速和有用的回复：

参考Timo Hahn的注释，我将数据插入列，然后用下面的查询执行，并且它工作。

  ALTER TABLE Product_Details 
 ADD CONSTRAINT pk_Product_Detils_Product_Detail_ID主键（Product_Detail_ID）
 GO 
 

谢谢大家

I am trying to add primary key to newly added column in existing table name Product_Details.

New Column added: Product_Detail_ID (int and not null)

I am trying add primary key to Product_Detail_ID (please note: there are no other primary or foreign key assigned to this table)

I am trying with this query but getting error.

ALTER TABLE Product_Details
ADD CONSTRAINT pk_Product_Detils_Product_Detail_ID PRIMARY KEY(Product_Detail_ID)
GO

Error:

The CREATE UNIQUE INDEX statement terminated because a duplicate key was found for the object name 'dbo.Product\_Details' and the index name 'pk\_Product\_Detils'. The duplicate key value is (0).

Am I missing something here? I am using SQL Server 2008 R2. I would appreciate any help.

I thank all of you for your prompt and helpful reply:

With reference of Timo Hahn's comment I insert the data into column and then execute with following query and it worked.

ALTER TABLE Product_Details
ADD CONSTRAINT pk_Product_Detils_Product_Detail_ID primary key(Product_Detail_ID)
GO

Thank you all