The following code can convert all columns into one for any table in the current db. The table should not contain image and timestamp columns. You can easily change the code to exclude those columns if it has.
USE NorthWind
GO
DECLARE @Col nvarchar(4000)
DECLARE @Table nvarchar(128)
DECLARE @Delimiter nvarchar(1)
-- Take dbo.Customers as example
-- @Delimiter can be empty string if not required, i.e. SET @Delimiter=''
SELECT @Col=N'',@Table='dbo.Customers',@Delimiter=';'
SELECT @Col=@Col+'CAST(ISNULL('+name+','''') AS nvarchar(4000))+'''+@Delimiter+'''+' FROM syscolumns where ID=OBJECT_ID(@Table)
SET @Col=LEFT(@Col,Len(@Col)-4-LEN(@Delimiter))
--PRINT @Col
EXEC ('SELECT '+@Col+' AS Output FROM '+@Table)