I recently got into a discussion with a colleague that was interesing. He
is a database warehouse guy, so I assume he knows more than I do on this
subject, but he was unable to explain things to me very well :)
The question is how does mysql organize data between the physical table, the
select statement and auto_increment?
As an example, if I insert one new row per second into a table with
auto_increment not null set, I had thought that when I make a select all
(not ordered) that the resulting data set would be in SOME kind of order.
In this paradigm, my colleague says that there are no guarantees that the
records will be retrieved in any kind of order, and may in fact be random.
How does this work?
He also states that auto_increment does not guarantee consistent increments.
All it does is guarantee increasing increments. So in fact what he says is
that if I insert 5 new records into an empty table with id as
auto_increment, the corresponding ids may be 1,5,7,23,24... or
10,19,21,30,43, etc...
I had thought that auto_increment incremented by 1, assuming the paradigm
described above, and no deletes from the table.
His reasoning for both of these examples is that the data may be written to
any physical location, and therefore retrieved in any order. I am a bit
suspicious of this, as I had thought that the new data in a table was
appended to the table (again using the paradigm above as the case).
Any thoughts on this stuff?
Thanks,
Bryan
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