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()
The data in the table is like this:
select hora,remota_id,caudal from historicos;
hora | remota_id | caudal
---------------------+-----------+----------
2010-05-21 20:00:06 | 04 | 1201.309
2010-05-21 20:15:08 | 04 | 1201.309
2010-05-21 20:30:06 | 04 | 1219.803
2010-05-21 20:45:06 | 04 | 1225.098
2010-05-21 21:00:06 | 04 | 1238.359
2010-05-21 21:15:06 | 04 | 1241.015
2010-05-21 21:30:06 | 04 | 1241.015
2010-05-21 21:45:06 | 04 | 1246.33
2010-05-21 22:00:06 | 04 | 1248.989
2010-05-21 22:15:06 | 04 | 1235.704
2010-05-21 22:30:06 | 04 | 1222.45
2010-05-21 22:45:06 | 04 | 1201.309
2010-05-21 23:00:06 | 04 | 1203.947
2010-05-21 23:15:06 | 04 | 1219.803
2010-05-21 23:30:06 | 04 | 1275.649
2010-05-21 23:45:06 | 04 | 1280.995
2010-05-22 00:00:06 | 04 | 1294.38
2010-05-22 00:15:06 | 04 | 1299.742
2010-05-22 00:30:06 | 04 | 1294.38
2010-05-22 00:45:06 | 04 | 1294.38
2010-05-22 01:00:06 | 04 | 1299.742
Can anyone help me?
Best,
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