Select corresponding value from second table (Mysql) - mysql

Question

Struggling with some sql, would appreciate some guidance.
Have two tables logs and sense
logs –
assetid ts nodeid status
1 2017-10-26 14:00:10 73 240
2 2017-10-26 14:00:06 21 160
3 2017-10-26 14:00:04 18 230
4 2017-10-26 14:00:02 19 400
5 2017-10-26 14:00:00 21 190
1 2017-10-26 13:20:08 18 20
2 2017-10-26 13:06:10 20 160
3 2017-10-26 13:03:04 17 230
sense –
status value
20 5
160 37
190 39
230 56
240 58
400 90
Trying to find the correct syntax to only show the latest record (in datetime) of each assetid and then show the corresponding value from the sense table (based on the matching status in both tables) to produce –
assetid ts nodeid status value
1 2017-10-26 14:00:10 73 240 58
2 2017-10-26 14:00:06 21 160 37
3 2017-10-26 14:00:04 18 230 56
4 2017-10-26 14:00:02 19 400 90
5 2017-10-26 14:00:00 21 190 39
Have tried –
Select assetid, ts, nodeid, status, value
From
logs
Join sense X on X.status = logs.status
Group by assetid
Order by ts DESC
But this only outputs 1 row (instead of 5)
assetid ts nodeid status value
1 2017-10-26 14:00:10 73 240 58
Removing
Join sense X on X.status = logs.status
of course outputs all records but that is not required.
Thoughts appreciated.
Regards
Active

Answer 1

Actually your query is returning 5 rows, 1 for each id. But it won't return rows with latest ts for each id. You can verify this by clicking on the link for demo. You can compare results of both queries.
To achieve this task,following query will help you:
Select l.assetid, l.ts, logs.nodeid, X.status, X.value
From
logs
inner Join sense X on X.status = logs.status
inner join (select assetid, max(ts) as ts from logs group by assetid) l
on l.assetid = logs.assetid and logs.ts = l.ts
Group by l.assetid
Order by l.ts DESC;
Click here for Demo
EDIT:
If dataype of ts is string then replace max(ts) in above query with:
max(str_to_date(ts,'%d%m%y'))
Feel free to ask any doubts.
Hope it helps!

Answer 2

Try this
Select a1.assetid, MAX(a1.ts), a1.nodeid, a1.status, X.value
From
logs a1
inner join sense X on X.status = a1.status
Group by assetid, a1.nodeid, a1.status, X.value
Order by ts DESC

Answer 3

Use GROUP BY to find minimum for each assetid and then JOIN with the logs and sense
Select *
FROM logs l
JOIN sense s ON s.status = l.status
JOIN
(
Select assetid, max(ts) maxts
From logs
Group by assetid
) t ON t.assetid = l.assetid and l.ts = t.maxts
demo

Answer 4

On MY SQL 8.0.2
WITH CTE as
(
Select A.assetid, A.ts, A.nodeid, A.status, B.value, row_number() over(PARTITION BY A.assetid ORDER BY A.ts DESC) AS rn
from logs as A
inner join sense B ON A.status=B.status
)
SELECT *
FROM CTE
WHERE rn='1';