Select from SQL database information with newest revisions - mysql

Question

I coding web app for my client and have issue with selecting from database raports with newest revisions.
SELECT
raports.*,
r1.*,
users.*,
(SELECT COUNT(*) FROM changes WHERE changes.changes_raports_id = raports.raports_id) as changes,
(SELECT changes.changes_date FROM changes WHERE changes.changes_raports_id = raports.raports_id ORDER BY changes.changes_date DESC LIMIT 1) as last_change,
(SUM(injuries.injuries_min_procent) / COUNT(injuries_to_raports.injuries_to_raports_id)) as min,
(SUM(injuries.injuries_max_procent) / COUNT(injuries_to_raports.injuries_to_raports_id)) as max
FROM raports
LEFT JOIN users
ON users.users_id = raports.raports_users_id
LEFT JOIN changes
ON changes.changes_raports_id = raports.raports_id
LEFT JOIN raports_to_changes r1
ON r1.raports_to_changes_raports_id = raports.raports_id
LEFT JOIN injuries_to_raports
ON injuries_to_raports.injuries_to_raports_raports_id = r1.raports_to_changes_raports_id
LEFT JOIN injuries
ON injuries_to_raports.injuries_to_raports_injuries_id = injuries.injuries_id
WHERE r1.raports_to_changes_changes_id = (SELECT max(raports_to_changes_changes_id) FROM raports_to_changes r2 WHERE r2.raports_to_changes_raports_id = r1.raports_to_changes_raports_id)
GROUP BY raports.raports_id ORDER BY raports.raports_id ASC;
In columns max and min i have not correct average from injuries. When i checked it and count all injuries i had 36 when true number is 2 but i have 18 revisions. So is logic that i have looped COUNT with all revisions but i want only the newest
I try changing WHERE statements and more LEFT JOINs but nothing helped.
Could someone fixed that code?
Thank you in advanced

Answer 1

Based on the clues revealed by your queries, the data model may look like this:
The select list shows that you need:
users information of a reports_id
aggregated injuries_min_procent and injuries_max_procent at raports_id level. (see cte_raport_injuries)
number of changes of a raports_id (see cte_raport_changes)
the last change_date of a raports_id (see cte_raport_changes)
I'm not sure about the need for raports_of_changes based on information revealed in the question, so I'm going to ignore it for now.
with cte_raport_injuries as (
select r.raports_id,
sum(i.injuries_min_procent) / count(*) as injuries_min_procent,
sum(i.injuries_max_procent) / count(*) as injuries_max_procent
from raports r
join injuries_to_raports ir
on r.raports_id = ir.injuries_to_raports_raports_id
join injuries i
on ir.injuries_to_raports_injuries_id = i.injuries_id
group by r.raports_id),
cte_raport_changes as (
select r.raports_id,
count(c.changes_id) as changes,
max(c.changes_date) as last_change
from raports r
join changes c
on r.raports_id = c.changes_raports_id
group by r.raports_id)
select u.users_id,
r.raports_id,
ri.injuries_min_procent,
ri.injuries_max_procent,
rc.changes,
rc.last_change
from raports r
join users u
on r.raports_users_id = u.users_id
join cte_raport_injuries ri
on r.raports_id = ri.raports_id
join cte_raport_changes rc
on r.raports_id = rc.raports_id;
The result looks like this:
users_id|raports_id|injuries_min_procent|injuries_max_procent|changes|last_change|
--------+----------+--------------------+--------------------+-------+-----------+
1| 11| 15.0000| 25.0000| 2| 2022-12-02|
So my question for you is what's in reports_to_changes that you need and what's its relationship between others? For further involvement from the community, you may want to share the following information in text format:
DDLs of each tables (primary key, foreign key, column names & data types)
Some representable sample data and basic business rules
Expected output