Sounds like you have a table (lkup_info) of load dates (date), in which you
record fileid (did) and date. Sounds like you do not have a separate table
of fileids. I'm assuming that the lkup_info table is updated synchronously
with the loading of each file that the table is recording, though you
didn't say that.
If this table also had an auto-increment numeric primary key
(lkup_info_id), and if we had a MySQL version that is still only a gleam in
Monty's eye, it would be a piece of cake:
SELECT * FROM lkup_info a
WHERE a.lkup_info_id IN
(SELECT MAX(lkup_info_id)
FROM lkup_info b
GROUP BY did)
In the absence of sub-selects, you will need to do the subsidiary select as
a preliminary step, INTO a temporary table. Then do the main select.
The pain of modifying the query to work without an auto-increment primary
key, and of waiting (and waiting, and waiting) for it to run, will be far
worse than the pain of adding an auto-increment primary key if one is not
already there.
Of course, if the table is not being updated synchronously with loading of
the files, all this is probably a pipe dream, for which I apologize.
--Erv
At 02:06 PM 1/24/2002 -0500, Anthony R. J. Ball wrote:
> Is it possible to select only the latest entries
>from a table?
>
> For instance I have a table of datasets that get
>loaded each day. I want to find the latest date that
>each dataset was loaded.
>
> I thought maybe a join against itself might be the
>answer, but this doesn't seem to work :)
>
>SELECT B.*
>from lkup_info AS A, lkup_info AS B
>WHERE A.did = B.did AND MAX(A.date) = B.date GROUP BY A.did;
>
> But that is basically what I want...
>
> Is this possible, or do I need to maintain a
>table for latest updates?
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