SQL 2008 R2 date query

try,

;WITH CTE AS (
        SELECT * FROM (
                SELECT C.Id AS CID,C.SaleDate AS CSaleDate,P.Id AS PID,P.SaleDate AS PSaleDate  FROM @Test C 
                LEFT OUTER JOIN
                @Test P ON C.Id = P.ID + 1
                WHERE ABS(DATEDIFF(ms,P.SaleDate,C.SaleDate)) <= 500 OR ABS(DATEDIFF(ms,P.SaleDate,C.SaleDate)) IS NULL
        ) X
), CTE1 AS (
        SELECT * FROM @Test WHERE ID IN (SELECT CID AS ID FROM CTE 
                                        UNION 
                                        SELECT PID AS ID FROM CTE)
)
SELECT * FROM CTE1

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Regards, RSingh