CREATE TABLE Person (

-- maybe Person is an Australian and maybe Australian has TFN,
AustralianTFN                           char(9) NULL,
-- maybe Person is an Employee and Employee has Employee ID,
EmployeeID                              int NULL,
-- Person has Person Name,
PersonName                              varchar NOT NULL,
PRIMARY KEY(PersonName)

) GO

CREATE VIEW dbo.AustralianInPerson_TFN (AustralianTFN) WITH SCHEMABINDING AS

SELECT AustralianTFN FROM dbo.Person
WHERE   AustralianTFN IS NOT NULL

GO

CREATE UNIQUE CLUSTERED INDEX IX_AustralianInPersonByAustralianTFN ON dbo.AustralianInPerson_TFN(AustralianTFN) GO

CREATE VIEW dbo.EmployeeInPerson_ID (EmployeeID) WITH SCHEMABINDING AS

SELECT EmployeeID FROM dbo.Person
WHERE   EmployeeID IS NOT NULL

GO

CREATE UNIQUE CLUSTERED INDEX PK_EmployeeInPerson ON dbo.EmployeeInPerson_ID(EmployeeID) GO