问题:

I need to be able to determine the order which rows have been inserted into a table (there are no updates). Can I use an identity column to do this? I know that there may be gaps, but are the values guaranteed to be increasing by insertion order?

回答1:

Largely yes, as long as you don't ever reset it or insert rows with bulk copy, or use IDENTITY_INSERT. And of course assuming that you don't overflow the data-type (which could be impressive).

回答2:

Yes. Any gaps caused by deletions will not be reused

回答3:

As discussed by Marc, yes you can with provisos

What you should do however to definitively fix the problem is add a column

dteInserted datetime not null default getdate()

Then you just select ordered by this.

Myself I automatically add such a column onto any 'data' table in any database I'm designing. Storage is cheap nowadays and timestamping the insertion date on a row is always useful at some point.