Unique Constraint: Enforce uniqueness on a column which is not the column used to primarily identify each row. : Unique « Constraints « SQL Server / T-SQL Tutorial
7.10.3.Unique Constraint: Enforce uniqueness on a column which is not the column used to primarily identify each row.
5> CREATE TABLE Employee (
6> EmployeeID Int IDENTITY(1,1) NOT NULL
7> , LastName nVarChar(50) NOT NULL
8> , FirstName nVarChar(50) NOT NULL
9> , SSN Char(9) NOT NULL)
10> GO
1>
2>
3> drop table Employee;
4> GO
1>