How can I select rows with most recent timestamp for each key value?

For the sake of completeness, here’s another possible solution:

SELECT sensorID,timestamp,sensorField1,sensorField2 
FROM sensorTable s1
WHERE timestamp = (SELECT MAX(timestamp) FROM sensorTable s2 WHERE s1.sensorID = s2.sensorID)
ORDER BY sensorID, timestamp;

Pretty self-explaining I think, but here’s more info if you wish, as well as other examples. It’s from the MySQL manual, but above query works with every RDBMS (implementing the sql’92 standard).