Data Sequence

Please try:

DECLARE @myTable TABLE (CustomerNumber INT, CustomerType VARCHAR(10), DateStampDatetime SMALLDATETIME) 
INSERT INTO @myTable 
SELECT 67, 'M2', '8/1/2009' UNION ALL 
SELECT 67, 'M2', '9/1/2009' UNION ALL 
SELECT 67, 'M2', '10/1/2009' UNION ALL 
SELECT 67, 'M2', '3/1/2009' UNION ALL 
SELECT 67, 'M1', '2/1/2009' UNION ALL 
SELECT 67, 'M1', '1/1/2009' UNION ALL 
SELECT 67, 'M1', '12/1/2008' UNION ALL 
SELECT 67, 'M1', '11/1/2008' 

;WITH CTE 
AS
(
        SELECT *
                ,ROW_NUMBER() OVER(PARTITION BY CustomerNumber, CustomerType ORDER BY DateStampDatetime ASC) AS Row_ASC
                ,ROW_NUMBER() OVER(PARTITION BY CustomerNumber, CustomerType ORDER BY DateStampDatetime DESC) AS Row_DSC
        FROM 
                @myTable 
)
SELECT 
        CustomerNumber 
        ,CustomerType 
        ,MAX(CASE WHEN Row_ASC = 1 THEN DateStampDatetime ELSE NULL END) As FromDate 
        ,MAX(CASE WHEN Row_DSC = 1 THEN DateStampDatetime ELSE NULL END) As ToDate 
FROM 
        CTE 
WHERE 
        Row_ASC = 1 
        OR Row_DSC = 1 
GROUP BY 
        CustomerNumber 
        ,CustomerType 

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Best Wishes, Arbi; Please vote if you find this posting was helpful or Mark it as answered.