Difference Between Primary Key and Foreign Key in SQL

Difference Between Primary Key and Foreign Key 

	Primary Key	Foreign Key
1	Primary Key Can Not Accept Null Values.	Foreign Key Can Accept Multiple Null Values.
2	Only One Primary Key in a Table.	More than One Foreign Key in a Table.
3	Primary Key Uniquely Identify a Record in the Table	Foreign Key is a Field in the Table that is Primary Key in Another Table
4	Primary Key is Clustered Index. Ex: CREATE TABLE [country] (     [id]      INT          IDENTITY (1, 1) NOT NULL,        [name] VARCHAR (50) NOT NULL,     UNIQUE NONCLUSTERED ([name],     CONSTRAINT [PK_country] PRIMARY KEY CLUSTERED ([id]) );	Foreign Key is Non-Clustered Index. Ex: CREATE TABLE [reg] (        [country]  VARCHAR (50) NOT NULL,     [name]     VARCHAR (50) NOT NULL,     CONSTRAINT [FK_reg_country] FOREIGN KEY ([name]) REFERENCES [dbo].[country] ([name]) );