Unique Constraint in SQL Server

What are Unique constraints in SQL Server?

Unique constraints uniquely identifies each records in a database


Syntax

CREATE TABLE Table_name(
    column1 Datatype1 NOT NULL,
    column2 Datatype2  NOT NULL,
    column3 Datatype3  NOT NULL,
    column4 Datatype4 ,
UNIQUE(columnname));
Example

CREATE TABLE Table_name(
    EmpID Int NOT NULL,
    Emp_Name Varchar(200)  NOT NULL,
    Address Varchar(200)  NOT NULL,
    Age int,
UNIQUE(EmpId));