Go4Expert - Primary key VS Unique key in SQL Server

Unique Key constraints:

Unique key constraint will provide you a constraint like the column values should retain uniqueness.
It will allow null value in the column.
It will create non-clustered index by default
Any number of unique constraints can be added to a table.

Code:

CREATE TABLE EMPLOYEETABLE

        (EMPID INT ,

         IDVAL INT NOT NULL,  

         FIRSTNAME VARCHAR(30) ,

         LASTNAME VARCHAR(30) ,

         CITY VARCHAR(30),

         JOININGDATE DATETIME)

I have created a table EmployeeTable and i am trying add a unique constriant on the column IDVAL.

Code:

 ALTER TABLE EMPLOYEETABLE

 ADD CONSTRAINT UNIQUE_CONSTRAINT 

 UNIQUE (IDVAL)

Primary Key:
Primary key will create column data uniqueness in the table.
Primary key will create clustered index by default
Only one Primay key can be created for a table
Multiple columns can be consolidated to form a single primary key
It wont allow null values.

Code:

 ALTER TABLE EMPLOYEETABLE

 ADD CONSTRAINT KEY_CONSTRAINT 

 PRIMARY KEY (IDVAL)

Please provide me your valuable feedback regarding this article.

Regards,
Venkatesan Prabu . J