DISTINCT と他の複数の選択された列を含む一意のセットを返します

WITH    q AS
        (
        SELECT  *,
                ROW_NUMBER() OVER (PARTITION BY dbo.[1_MAIN - Contacts].Contact_ID ORDER BY dbo.[1_MAIN - Contacts].Contact_ID) AS rn
        FROM    dbo.[1_MAIN - Contacts]
        INNER JOIN
                dbo.Referral
        ON      dbo.[1_MAIN - Contacts].Contact_ID = dbo.Referral.Referral_ID
        INNER JOIN
                dbo.prov_training_records
        ON      dbo.[1_MAIN - Contacts].Contact_ID = dbo.prov_training_records.Contact_ID
        LEFT OUTER JOIN
                dbo.Resource_Center
        ON      dbo.[1_MAIN - Contacts].Contact_ID = dbo.Resource_Center.Contact_ID
        FULL OUTER JOIN
                dbo.Providers
        ON      dbo.[1_MAIN - Contacts].Contact_ID = dbo.Providers.Contact_ID
        )
SELECT  *
FROM    q
WHERE   rn = 1