Re: Help with select with max and min please

  El 08/08/10 21:49, Edoardo Panfili escribió:
> On 08/08/10 20.47, Jose Maria Terry wrote:
>> Hello all,
>>
>> I need to run a query on a table that holds logged data from several
>> water flow meters.
>>
>> I need the first and last values (with their associated time) for every
>> logger in a time range.
>>
>> I've tried this that returns the min and max time in the desired range
>> for every logger, but i don't know how to get the associated data (the
>> row called caudal) for min and max .
>>
>> select remota_id,min(hora),max(hora) from historicos where hora >
>> '2010-08-07' and hora <'2010-08-08 00:03' group by remota_id order by
>> remota_id;
>>
>> remota_id | min | max
>> -----------+---------------------+---------------------
>> 01 | 2010-08-07 00:00:30 | 2010-08-08 00:00:30
>> 02 | 2010-08-07 00:00:06 | 2010-08-08 00:00:06
>> 03 | 2010-08-07 00:00:03 | 2010-08-08 00:00:02
>> 04 | 2010-08-07 00:00:06 | 2010-08-08 00:00:06
>> 05 | 2010-08-07 00:00:01 | 2010-08-08 00:00:02
>> 06 | 2010-08-07 00:00:02 | 2010-08-08 00:00:02
>> 07 | 2010-08-07 00:00:06 | 2010-08-08 00:00:06
>> 09 | 2010-08-07 00:00:06 | 2010-08-08 00:00:06
>> (8 filas)
>>
>> I need some like this:
>>
>> remota_id | min | max | min_caudal | max_caudal
>> -----------+---------------------+---------------------+------------+------------
>>
>>
>> 01 | 2010-08-07 00:00:30 | 2010-08-08 00:00:30 | 976.04 | 904.21
>> 02 | 2010-08-07 00:00:06 | 2010-08-08 00:00:06 | 829.71 | 764.42
>>
>> Where min_caudal is the value of caudal in hora = min() and max_caudal
>> is the same for hora=max()
>
> this can help?
> select remota_id,min(hora),max(hora), (SELECT caudal FROM historicos
> WHERE remota_id=ooo.remota_id AND hora=min(ooo.hora)) as min_caudal,
> (SELECT caudal FROM historicos WHERE remota_id=ooo.remota_id AND
> hora=max(ooo.hora)) as max_caudal from historicos AS ooo group by
> remota_id order by remota_id;
>
> Edoardo

Thanks, Edoardo!

Works perfect, i've added the date (hora) select and the result is just
what expected:

select remota_id,min(hora),max(hora), (SELECT caudal FROM historicos
WHERE remota_id=ooo.remota_id AND hora=min(ooo.hora)) as min_caudal,
(SELECT caudal FROM historicos WHERE remota_id=ooo.remota_id AND
hora=max(ooo.hora)) as max_caudal from historicos AS ooo where hora >
'2010-08-07' and hora <'2010-08-08 00:03' group by remota_id order by
remota_id;

  remota_id |         min         |         max         | min_caudal |
max_caudal
-----------+---------------------+---------------------+------------+------------
  01        | 2010-08-07 00:00:30 | 2010-08-08 00:00:30 |   2785.727 |
2766.883
  02        | 2010-08-07 00:00:06 | 2010-08-08 00:00:06 |   1820.309 |
1860.785
  03        | 2010-08-07 00:00:03 | 2010-08-08 00:00:02 |   2296.633 |
2280.154
  04        | 2010-08-07 00:00:06 | 2010-08-08 00:00:06 |   1946.548 |
1898.955
  05        | 2010-08-07 00:00:01 | 2010-08-08 00:00:02 |   664.5776 |
984.9826
  06        | 2010-08-07 00:00:02 | 2010-08-08 00:00:02 |    1103.71
|    1185.17
  07        | 2010-08-07 00:00:06 | 2010-08-08 00:00:06 |   452.0654 |
410.4259
  09        | 2010-08-07 00:00:06 | 2010-08-08 00:00:06 |   766.8262 |
774.8085
(8 filas)


Best


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