On 5 July 2010 16:26, Pedro Zorzenon Neto <pedro2009@mandic.com.br> wrote:
>> I'm probably misunderstanding the problem, but can't you just do:
>>
>> SELECT
>> diag_value
>> FROM
>> diagnose_logs
>> WHERE
>> ts <= '2009-12-25 23:59:59'
>> AND
>> hardware_id BETWEEN 1 AND 500
>> ORDER BY
>> ts DESC
>> LIMIT 1
>
> Hi Thom,
>
> Yes, I think you misunderstood.
>
> An example of a table:
>
> hardware_id | ts | diag_value
> 1 | 2009-12-25 14:00:00 | 43.5 (*)
> 1 | 2009-12-26 15:00:00 | 43.6
> 1 | 2009-12-24 13:00:00 | 43.7
> 2 | 2009-12-24 15:00:00 | 43.8 (*)
> 2 | 2009-12-24 14:00:00 | 43.9
> 2 | 2009-12-24 14:16:00 | 43.9
> 2 | 2009-12-27 14:00:00 | 44.0
>
> I need to get the "most recent" value before "2009-12-25 23:59:59" from
> every hardware_id.
>
> For hardware_id=1, the value would be:
> 1 | 2009-12-25 14:00:00 | 43.5
> for hardware_id=2, the value would be:
> 2 | 2009-12-24 15:00:00 | 43.8
>
> I need a query that will return me those lines marked with (*) :-) is
> this possible?
>
> Thanks!
>
>
D'oh! I completely ignored that "LIMIT 1". okay... what Sam said.
Thom