How to copy a huge table data into another table in SQL Server

I had the same problem, except I have a table with 2 billion rows, so the log file would grow to no end if I did this, even with the recovery model set to Bulk-Logging:

insert into newtable select * from oldtable

So I operate on blocks of data. This way, if the transfer is interupted, you just restart it. Also, you don't need a log file as big as the table. You also seem to get less tempdb I/O, not sure why.

set identity_insert newtable on
DECLARE @StartID bigint, @LastID bigint, @EndID bigint
select @StartID = isNull(max(id),0) + 1
from newtable

select @LastID = max(ID)
from oldtable

while @StartID < @LastID
begin
    set @EndID = @StartID + 1000000

    insert into newtable (FIELDS,GO,HERE)
    select FIELDS,GO,HERE from oldtable (NOLOCK)
    where id BETWEEN @StartID AND @EndId

    set @StartID = @EndID + 1
end
set identity_insert newtable off
go

You might need to change how you deal with IDs, this works best if your table is clustered by ID.

If you are copying into a new table, the quickest way is probably what you have in your question, unless your rows are very large.

If your rows are very large, you may want to use the bulk insert functions in SQL Server. I think you can call them from C#.

Or you can first download that data into a text file, then bulk-copy (bcp) it. This has the additional benefit of allowing you to ignore keys, indexes etc.

Also try the Import/Export utility that comes with the SQL Management Studio; not sure whether it will be as fast as a straight bulk-copy, but it should allow you to skip the intermediate step of writing out as a flat file, and just copy directly table-to-table, which might be a bit faster than your SELECT INTO statement.