DECLARE @table TABLE(value NVARCHAR(30), fieldName Varchar(10))
INSERT INTO @table VALUES('Jan 29 2013 12:00AM', 'pur_date'), ('afvajfab', 'sft_name')
SELECT
CASE WHEN fieldName = 'pur_date' THEN CONVERT(VARCHAR(32),CAST([value] AS DATETIME),101)
ELSE value END
FROM @table