Select most recent record grouped by 3 columns - mysql

Question

I am trying to return the price of the most recent record grouped by ItemNum and FeeSched, Customer can be eliminated. I am having trouble understanding how I can do that reasonably.
The issue is that I am joining about 5 tables containing hundreds of thousands of rows to end up with this result set. The initial query takes about a minute to run, and there has been some trouble with timeout errors in the past. Since this will run on a client's workstation, it may run even slower, and I have no access to modify server settings to increase memory / timeouts.
Here is my data:
Customer Price ItemNum FeeSched Date
5 70.75 01202 12 12-06-2017
5 70.80 01202 12 06-07-2016
5 70.80 01202 12 07-21-2017
5 70.80 01202 12 10-26-2016
5 82.63 02144 61 12-06-2017
5 84.46 02144 61 06-07-2016
5 84.46 02144 61 07-21-2017
5 84.46 02144 61 10-26-2016
I don't have access to create temporary tables, or views and there is no such thing as a #variable in C-tree, but in most ways it acts like MySql. I wanted to use something like GROUP BY ItemNum, FeeSched and select MAX(Date). The issue is that unless I put Price into the GROUP BY I get an error.
I could run the query again only selecting ItemNum, FeeSched, Date and then doing an INNER JOIN, but with the query taking a minute to run each time, it seems there is a better way that maybe I don't know.
Here is my query I am running, it isn't really that complicated of a query other than the amount of data it is processing. Final results are about 50,000 rows. I can't share much about the database structure as it is covered under an NDA.
SELECT DISTINCT
CustomerNum,
paid as Price,
ItemNum,
n.pdate as newest
from admin.fullproclog as f
INNER JOIN (
SELECT
id,
itemId,
MAX(TO_CHAR(pdate, 'MM-DD-YYYY')) as pdate
from admin.fullproclog
WHERE pdate > timestampadd(sql_tsi_year, -3, NOW())
group by id, itemId
) as n ON n.id = f.id AND n.itemId = f.itemId AND n.pdate = f.pdate
LEFT join (SELECT itemId AS linkid, ItemNum FROM admin.itemlist) AS codes ON codes.linkid = f.itemId AND ItemNum >0
INNER join (SELECT DISTINCT parent_id,
MAX(ins1.feesched) as CustomerNum
FROM admin.customers AS p
left join admin.feeschedule AS ins1
ON ins1.feescheduleid = p.primfeescheduleid
left join admin.group AS c1
ON c1.insid = ins1.feesched
WHERE status =1
GROUP BY parent_id)
AS ip ON ip.parent_id = f.parent_id
WHERE CustomerNum >0 AND ItemNum >0
UNION ALL
SELECT DISTINCT
CustomerNum,
secpaid as Price,
ItemNum,
n.pdate as newest
from admin.fullproclog as f
INNER JOIN (
SELECT
id,
itemId,
MAX(TO_CHAR(pdate, 'MM-DD-YYYY')) as pdate
from admin.fullproclog
WHERE pdate > timestampadd(sql_tsi_year, -3, NOW())
group by id, itemId
) as n ON n.id = f.id AND n.itemId = f.itemId AND n.pdate = f.pdate
LEFT join (SELECT itemId AS linkid, ItemNum FROM admin.itemlist) AS codes ON codes.linkid = f.itemId AND ItemNum >0
INNER join (SELECT DISTINCT parent_id,
MAX(ins1.feesched) as CustomerNum
FROM admin.customers AS p
left join admin.feeschedule AS ins1
ON ins1.feescheduleid = p.secfeescheduleid
left join admin.group AS c1
ON c1.insid = ins1.feesched
WHERE status =1
GROUP BY parent_id)
AS ip ON ip.parent_id = f.parent_id
WHERE CustomerNum >0 AND ItemNum >0

Answer 1

I feel it quite simple when I'd read the first three paragraphs, but I get a little confused when I've read the whole question.
Whatever you have done to get the data posted above, once you've got the data like that it's easy to retrive "the most recent record grouped by ItemNum and FeeSched".
How to:
Firstly, sort the whole result set by Date DESC.
Secondly, select fields you need from the sorted result set and group by ItemNum, FeeSched without any aggregation methods.
So, the query might be something like this:
SELECT t.Price, t.ItemNum, t.FeeSched, t.Date
FROM (SELECT * FROM table ORDER BY Date DESC) AS t
GROUP BY t.ItemNum, t.FeeSched;
How it works:
When your data is grouped and you select rows without aggregation methods, it will only return you the first row of each group. As you have sorted all rows before grouping, so the first row would exactly be "the most recent record".
Contact me if you got any problems or errors with this approach.

Answer 2

You can also try like this:
Select Price, ItemNum, FeeSched, Date from table where Date IN (Select MAX(Date) from table group by ItemNum, FeeSched,Customer);
Internal sql query return maximum date group by ItemNum and FeeSched and IN statement fetch only the records with maximum date.