Or with the sensor name included
select t1.sensor_id,s.naam,t1.temp_c
from temperature t1, sensor s
where t1.timestamp = (select max(t2.timestamp)
from temperature t2
where t1.sensor_id=t2.sensor_id)
and s.sensor_id=t1.sensor_id
11:30:15 29-CC1-JACK> select * from temperature
11:30:25 2 /
SENSOR_ID TEMP_C TIMESTAMP
---------- ---------- -----------------
1 15 18-jul-2002 09:25
2 16 18-jul-2002 09:25
1 11 18-jul-2002 09:25
2 18 18-jul-2002 09:25
3 17 18-jul-2002 09:25
1 15 18-jul-2002 09:25
2 15 18-jul-2002 09:25
3 15 18-jul-2002 09:25
1 11 18-jul-2002 09:25
2 12 18-jul-2002 09:25
3 110 18-jul-2002 09:25
2 12 18-jul-2002 09:30
3 110 18-jul-2002 09:30
1 11 18-jul-2002 09:30
14 rows selected.
11:30:26 29-CC1-JACK> select * from sensor
11:30:53 2 /
SENSOR_ID NAAM
---------- ------------------------------
1 sensor1
2 sensor2
3 sensor3
11:30:54 29-CC1-JACK> @xx
SENSOR_ID NAAM TEMP_C
---------- ------------------------------ ----------
1 sensor1 11
2 sensor2 12
3 sensor3 110
11:31:02 29-CC1-JACK>
"Jack van Zanen"
<[EMAIL PROTECTED]> To: Multiple recipients of list
ORACLE-L <[EMAIL PROTECTED]>
Sent by: cc: (bcc: Jack van
Zanen/nlzanen1/External/MEY/NL)
[EMAIL PROTECTED] Subject: Re: SQL Join or Subquery
18-07-2002 10:38
Please respond to
ORACLE-L
Hi
Try:
select t1.sensor_id,t1.temp_c
from temperature t1
where t1.timestamp = (select max(t2.timestamp)
from temperature t2
where t1.sensor_id=t2.sensor_id)
Jack
Gary Chambers
<[EMAIL PROTECTED]> To: Multiple
recipients of list ORACLE-L <[EMAIL PROTECTED]>
Sent by: cc: (bcc: Jack van
Zanen/nlzanen1/External/MEY/NL)
[EMAIL PROTECTED] Subject: SQL Join or
Subquery
17-07-2002 23:54
Please respond to
ORACLE-L
All...
I have a question about a query over which I've been racking my brain
for weeks, and I can't find a reference to adequately assist me.
Given a table of temperature sensors, and a table of readings from those
sensors, how might I grab the max (hence latest or current) temperature
reading for each sensor? The relevant fields in the tables are
timestamp and temp_c (temperature table), and sensorid (both temperature
and sensor tables).
I'm fairly certain that I'm overlooking something very elementary, and I
feel it should be simple and straightforward, but I think I'm being
stymied by the use of aggregate functions in my query. I can provide
examples of my failed attempts, if you'd like. Thanks in advance for
any assistance you can provide.
Gary Chambers
//-------------------------------------
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