In the last episode (Dec 27), Russ Lavoie said:
> I am currently upgrading from mysql 5.1.72 -> mysql 5.6 and the migration
> and upgrade is sound (In a QA ENV). Queries work etc. However, when I
> run a query similar to "SELECT `table`.* FROM `table` WHERE (credential_id
> IN (13528, 14906, 38845)) ORDER BY `date` DESC LIMIT 1;" on 5.1.72 and on
> 5.6.15 I get back different data. The date for all of the data are
> exactly the same to the second.
>
> However, if I run "SELECT `table`.* FROM `table` WHERE (credential_id IN
> (13528, 14906, 38845)) ORDER BY `date` LIMIT 1;" it comes back with the
> exact same data that is expected. Is this a bug? Or am I missing here?
It's probably a difference in the optimizer or the query engine between 5.1
and 5.6. Since you only specified "ORDER BY `date`", mysql is free to
return rows with the same date value in any order, even on consecutive runs
within the same session if it wants to. If you need a stable sort every
time, you'll need to add another column to your ORDER BY clause. `id` might
be a good choice (since it's your primary key for that table), or
credential_id (since you're using that in your WHERE clause already).
--
Dan Nelson
dnel...@allantgroup.com
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