I have this example table:
Machine_ID | ID | STATE
3210 | 543210 | ACTIVATION
3210 | 543789 | ACTIVE
1212 | 111111 | ACTIVE
1212 | 111222 | ACTIVE
4444 | 444444 | STOPPED
4444 | 555555 | STARTED
All i want to do is to get latest state of every machine (greater ID = later action)
Pseudocode:
foreach Machine_ID
select * where ID greatest
My output table should look like:
Machine_ID | ID | STATE
3210 | 543789 | ACTIVE
1212 | 111222 | ACTIVE
4444 | 555555 | STARTED
Thanks for help in advice. Please describe your solution, as many others can use it as well (i did not found following example in google or any tutorial). I use Oracle DB
You can get this using a keep
construct:
select machine_id, max(id),
max(state) keep (dense_rank first order by id desc) as laststate
from machines m
group by machine_id;
Wherever possible, you should always take a set based approach to processing data. In this case, you can do this by creating a derived table of the Max ID of each Machine ( GROUP
ed) and then JOIN
back to this derived table:
SELECT m.MachineID, m.ID, m.State
FROM Machine m
INNER JOIN
(
SELECT MachineID, MAX(ID) AS MaxID
FROM Machine
GROUP BY MachineID) x
ON m.MachineID = x.MachineID
AND m.ID = x.MaxID;
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