Yes, it is safe, even though it will seriously impact server performance
during the conversion, cost a lot of log space (temporarily). Also, you
should expect serious growth of the required space for the table, expect
the current table size * 2.

BTW, the simple test below proves the change is safe.

CREATE TABLE Test (a varchar(255))
INSERT INTO Test VALUES ('a')
INSERT INTO Test VALUES (REPLICATE('b',255))
INSERT INTO Test DEFAULT VALUES
SELECT * FROM Test
go
ALTER TABLE Test ALTER COLUMN a nvarchar(255)
go
SELECT * FROM Test
DROP TABLE Test

--
Gert-Jan


Danny wrote:
>
> Hi All,
>
> I have a varchar(255) column for storing text in english and in
> hebrew.
> It was a stupid mistake to set the data type to be varchar, because
> now I need to store text in german and francais too.
>
> Question: Is it safe to change the data type from varchar to nvarchar,
> without damaging the data that's already present?
> (I have more than 1000000 records stored...)
>
> Thanks,
> Danny