CREATE FUNCTION [dbo].[SearchContacts]
(
    @contactsKeyword nvarchar(4000)
)
RETURNS @returntable TABLE
(
    [KEY] int,
    [RANK] int
)
AS
BEGIN
    INSERT @returntable
    SELECT [KEY],[RANK] FROM CONTAINSTABLE(dbo.Contact, ([LastName],[FirstName],[Title]), @contactsKeyword)
    RETURN
END

SELECT
    [KEY] = x.KEY,
    [RANK] = ???
FROM [dbo].[SearchContacts](@keyword1) x
JOIN [dbo].[SearchContacts](@keyword2) y on x.KEY = y.KEY