SQL Server, Converting NTEXT to NVARCHAR(MAX)

Question

I have a database with a large number of fields that are currently NTEXT.

Having upgraded to SQL 2005 we have run some performance tests on converting these to NVARC

Answer 1

If you can't get scheduled downtime....

create two new columns: nvarchar(max) processedflag INT DEFAULT 0

Create a nonclustered index on the processedflag

You have UPDATE TOP available to you (you want to update top ordered by the primary key).

Simply set the processedflag to 1 during the update so that the next update will only update where the processed flag is still 0

You can use @@rowcount after the update to see if you can exit a loop.

I suggest using WAITFOR for a few seconds after each update query to give other queries a chance to acquire locks on the table and not to overload disk usage.