SQL Best Practices - Ok to rely on auto increment field to sort rows chronologically?

Question

I\'m working with a client who wants to add timestamps to a bunch of tables so that they may sort the records in those tables chronologically. All of the tables also have a

Answer 1

Further to egrunin's answer, a change to the persistence or processing logic of these rows may cause rows to be inserted into the database in a non-sequential or nondeterministic manner. You may implement a parallelized file processor that throws a row into the DB as soon as the thread finishes transforming it, which may be before another thread has finished processing a row that occurred earlier in the file. Using an ORM for record persistence may result in a similar behavior; the ORM may just maintain a "bag" (unordered collection) of object graphs awaiting persistence, and grab them at random to persist them to the DB when it's told to "flush" its object buffer.

In either case, trusting the autoincrement column to tell you the order in which records came into the SYSTEM is bad juju. It may or may not be able to tell you the order in which records his the DATABASE; that depends on the DB implementation.