Extract the file name part from a path in Transact SQL.
DECLARE @fileName as varchar(255)
SET @fileName = 'D:\dir1\dir2\file.txt'
PRINT @fileName -- D:\dir1\dir2\file.txt
-- REVERSE is used to get the last "\" of the string
SET @fileName = RIGHT(@fileName, CHARINDEX('\', REVERSE(@fileName))-1)
PRINT @fileName -- file.txt