SQL query MAX functions - sql

Question

I want to fetch data for a perticular product on basis of last user & respective last used time.Example
Host Product LastUserName LastUsedTime
1 X1 ABC 6/13/2014
1 X1 ABC 6/14/2014
1 X1 ABC 6/15/2014
1 X1 XYZ 6/14/2014
1 X1 XYZ 6/15/2014
1 X1 XYZ 6/16/2014
I have tried MAX function and find data as
Host Product LastUserName LastUsedTime
1 X1 ABC 6/15/2014
1 X1 XYZ 6/16/2014
But unable to get desired output which is
Host Product LastUserName LastUsedTime
1 X1 XYZ 6/16/2014
SQL:
select a.Netbios_Name0, b.DisplayName0, c.LastUserName0,
MAX(c.LastUsedTime0) as [Last Used Time]
from table1 a,table2 b,table3 c
where a.ItemKey = b.ResourceID
and a.ItemKey = c.ResourceID
group by a.Netbios_Name0, b.DisplayName0, c.LastUserName0
order by b.DisplayName0
Thanks for Help !!

Answer 1

For MSSQL :
select a.host, a.Product, a.LastUserName, a.LastUsedTime
from tablex a join
(
select Host, Product, max(LastUsedTime) as LastUsedTime
from tablex
group by Host, Product
) b on a.host = b.host and a.Product = b.Product and a.LastUsedTime = b.LastUsedTime

Answer 2

If you just want one row, don't use GROUP BY. Just order the results and use TOP 1 to get the first row (LIMIT 1 is for MySQL -- this is why you should always tell your RDBMS in questions).
select TOP 1 a.Netbios_Name0, b.DisplayName0, c.LastUserName0, c.LastUsedTime0
from table1 a,table2 b,table3 c
where a.ItemKey = b.ResourceID
and a.ItemKey = c.ResourceID
ORDER BY c.LastUsedTime0 DESC

Answer 3

Try this:
SELECT TOP 1 a.Netbios_Name0, b.DisplayName0, c.LastUserName0,
c.LastUsedTime0 as [Last Used Time]
FROM table1 a INNER JOIN
table2 b ON a.ItemKey = b.ResourceID INNER JOIN
table3 c ON a.ItemKey = c.ResourceID
WHERE c.LastUsedTime0 = (SELECT TOP 1 LastUsedTime0 FROM table3 WHERE ResourceID = c.ResourceID)

Answer 4

To get the row with the last date per product you first need to get that last date, then JOIN back to the others values
WITH L AS (
SELECT b.DisplayName0, MAX(c.LastUsedTime0) LastUsedTime0
FROM table2 b
INNER JOIN table3 c ON b.ResourceID = c.ResourceID
GROUP BY b.DisplayName0
)
SELECT a.Netbios_Name0, b.DisplayName0, c.LastUserName0
, c.LastUsedTime0 as [Last Used Time]
FROM table1 a
INNER JOIN table2 b ON a.ItemKey = b.ResourceID
INNER JOIN table3 c ON a.ItemKey = c.ResourceID
INNER JOIN L ON b.DisplayName0 = L.DisplayName0
AND c.LastUsedTime0 = L.LastUsedTime0
ORDER BY b.DisplayName0
if you need to separate also the host name you need to change the query to
WITH L AS (
SELECT a.Netbios_Name0, b.DisplayName0, MAX(c.LastUsedTime0) LastUsedTime0
FROM table1 a
INNER JOIN table2 b ON a.ItemKey = b.ResourceID
INNER JOIN table3 c ON a.ItemKey = c.ResourceID
GROUP BY a.Netbios_Name0, b.DisplayName0
)
SELECT a.Netbios_Name0, b.DisplayName0, c.LastUserName0
, c.LastUsedTime0 as [Last Used Time]
FROM table1 a
INNER JOIN table2 b ON a.ItemKey = b.ResourceID
INNER JOIN table3 c ON a.ItemKey = c.ResourceID
INNER JOIN L ON a.Netbios_Name0 = L.Netbios_Name0
AND b.DisplayName0 = L.DisplayName0
AND c.LastUsedTime0 = L.LastUsedTime0
ORDER BY b.DisplayName0
As a last advice please stop to write the JOIN definition in the WHERE clause, it's less readable and mix to different ideas

Answer 5

;with cte as
(
select max(lastusedtime) over (PARTITION by product) as mdate
,host,product,lastusername ,lastusedtime
from test1
)
select distinct host,product,lastusername ,lastusedtime from cte
where lastusedtime=mdate

Answer 6

SELECT Product_Usage.*
FROM Product_Usage
INNER JOIN (SELECT Product, max(LastUsedTime) LastUSedTime
FROM Product_Usage
GROUP BY Product) LastUsed
ON Product_Usage.Product = LastUsed.Product
AND Product_Usage.LastUsedTime = LastUsed.LastUsedTime

Answer 7

Try this:
SELECT TOP 1 * FROM table_name ORDER BY LastUsername DESC, LastUsedTime DESC