One way to go:

DECLARE @T TABLE (ID INT PRIMARY KEY, SentDate VARCHAR(10), ReceivedDate VARCHAR(10), CreatedDate VARCHAR(10))

INSERT INTO

@T

VALUES

(1, NULL, '2-11-2012', NULL),

(2, '22-10-2012', NULL, '2-12-2012'),

(3, '8-8-2012', NULL, NULL),

(4, NULL, NULL, '25-12-2012'),

(5, '7-11-2012', '1-8-2012','5-1-2012')

SET DATEFORMAT dmy

SELECT

ID, MAX(CAST(AnyDate AS DATE)) -- Select the maximum date out of the three splitted rows

FROM

@T

CROSS APPLY

(

-- Split row into three rows, each row containing a different date

VALUES (SentDate), (ReceivedDate), (CreatedDate)

) CA(AnyDate)

GROUP BY

ID

And I am totally agreeing with GSquared. I took the risk.

Edit: Added cast to date