Hi.
Due to various accidents we have ended up producing a table with
multiple entries for the same key (part of the accident is that the
index was not created to be unique...)
I would like to try writing a migration to delete out of date rows and
perhaps even make the index unique to avoid future issues of the same
sort.
I happened to notice that for my own database, the data appeared to be
in the order inserted, such that the correct row was always last. If
that is always the case, then I could scan through the whole table,
recording entries which are redundant, then scan through again to
delete the redundant entries. But this only works if I can guarantee
that it's always in that order.
In the Derby docs, there is text along these lines:
Note: Make sure to specify the ORDER BY clause if you expect
to retrieve a sorted result set. If you do not use an ORDER BY
clause, the result set that is retrieved will typically have the order
in which the records were inserted.
Here it says "typically", implying that in some situations this is not
the case. so I'm wondering in what situations it wouldn't come back in
this order.
TX
