Difference Between Primary Key and Unique Key in SQL

Difference Between Primary Key and Unique Key 

	Primary Key	Unique Key
1	Primary Key Can't Accept Null Values.	Unique Key Can Accept Only One Null Value
2	Creates Clustered Index	Creates Non-Clustered Index
3	Only One Primary key in a Table	More than One Unique Key in a Table.
4	Primary Key Can be Made Foreign Key Into Another Table. Ex: CREATE TABLE [country] (        [id]    VARCHAR (50) NOT NULL,     [country] VARCHAR (50) NOT NULL,          CONSTRAINT [PK_country] PRIMARY KEY CLUSTERED ([id]));	SQL Server, Unique Key Can be Made Foreign Key Into Another Table. Ex: CREATE TABLE [country] (         [name]    VARCHAR (50) NOT NULL,     [country] VARCHAR (50) NOT NULL,       UNIQUE NONCLUSTERED ([name]));