SQL Inner Join based on MAX of timestamp - sql

Question

Amended Once
Amended Twice: The headers of the remaining 9 tables except for reports are always called "what".
I have about 10 tables with the following structure:
reports (165k rows)
+-----------+-----------+
| identifier| category |
+-----------+-----------+
| 1 | fixed |
| 2 | wontfix |
| 3 | fixed |
| 4 | invalid |
| 5 | later |
| 6 | wontfix |
| 7 | duplicate |
| 8 | later |
| 9 | wontfix |
+-----------+-----------+
status (300k rows, all identifiers from reports come up at least once)
+-----------+-----------+----------+
| identifier| time | what |
+-----------+-----------+----------+
| 1 | 12 | RESOLVED |
| 1 | 9 | NEW |
| 2 | 7 | ASSIGNED |
| 3 | 10 | RESOLVED |
| 5 | 4 | REOPEN |
| 7 | 9 | ASSIGNED |
| 4 | 9 | ASSIGNED |
| 7 | 11 | RESOLVED |
| 8 | 3 | NEW |
| 4 | 3 | NEW |
| 7 | 6 | NEW |
+-----------+-----------+----------+
priority (300k rows, all identifiers from reports come up at least once)
+-----------+-----------+----------+
| identifier| time | what |
+-----------+-----------+----------+
| 3 | 12 | LOW |
| 1 | 9 | LOW |
| 9 | 2 | HIGH |
| 8 | 7 | HIGH |
| 3 | 10 | HIGH |
| 5 | 4 | MEDIUM |
| 4 | 9 | MEDIUM |
| 4 | 3 | LOW |
| 7 | 9 | LOW |
| 7 | 11 | HIGH |
| 8 | 3 | LOW |
| 6 | 12 | MEDIUM |
| 7 | 6 | LOW |
| 6 | 9 | HIGH |
| 2 | 6 | HIGH |
| 2 | 1 | LOW |
+-----------+-----------+----------+
What I need is:
reportsfinal (165k rows)
+-----------+-----------+--------------+------------+
| identifier| category | what11 | what22 |
+-----------+-----------+--------------+------------+
| 1 | fixed | RESOLVED | LOW |
| 2 | wontfix | ASSIGNED | HIGH |
| 3 | fixed | RESOLVED | LOW |
| 4 | invalid | ASSIGNED | MEDIUM |
| 5 | later | REOPEN | MEDIUM |
| 6 | wontfix | | MEDIUM |
| 7 | duplicate | RESOLVED | HIGH |
| 8 | later | NEW | HIGH |
| 9 | wontifx | | HIGH |
+-----------+-----------+--------------+------------+
That is, reports (after query = reportsfinal) serves as the basis table and I have to add one or two columns from 9 other tables. The identifier is the key, but in some tables, the identifier comes up multiple times. In these cases I want to use the entry with the highest time only.
I tried several queries, but none of them worked. If possible, I want to run one query to get different columns from the 9 other tables with this approach.
What I tried based on the answer below:
select T.identifier,
T.category,
t.what AS what11,
t.what AS what22 from (
select R.identifier,
R.category,
COALESCE(S.what,'NA')what,
COALESCE(P.what,'NA')what,
ROW_NUMBER()OVER(partition by R.identifier,R.category ORDER by (select null))RN
from reports R
LEFT JOIN bugstatus S
ON S.identifier = R.identifier
LEFT JOIN priority P
ON P.identifier = s.identifier
GROUP BY R.identifier,R.category,S.what,P.what)T
Where T.RN = 1
ORDER BY T.identifier;
This gives the error:
Error: near "(": syntax error.

Answer 1

Basically you need a correlated subqueries in the select list.
From the hip, something like:
Select a.Identifier
,a.Category
,(select process
from status where status.identifier = a.Identifer order by time desc limit 1) Process
,(select prio
from priority where priorty.identifier = a.Identifer order by time desc limit 1) prio
From Reports a

Answer 2

For each associated table just use a predicate based on a subquery to identify the specific timestamp...
Single letter tokens r, s, and p are defined aliases for tables reports, status and priority respectively
Select r.Identifier, r.category,
coalesce(s.what, 'NA') status,
coalesce(p.what, 'NA') priority
From reports r
left join status s
on s.identifier = r.identifier
and s.time =
(Select max(time) from status
where identifier = r.identifier)
left join priority p
on p.identifier = r.identifier
and p.time =
(Select max(time) from priority
where identifier = r.identifier);
QUESTION: Why did you rename the columns from Status, and priority to What?? You might as well name then something or data, or information. At least the original names (status and prio) communicated something.. The word What is meaningless.
NOTE. I reversed (undid) the edit for the aliases of what11 and what12, as these names are e meaningless.

Answer 3

using Row_number works based on your assumed data
select T.identifier,
T.category,
what AS what11,
what AS what22 from (
select R.identifier,
r.category,
COALESCE(S.what,'NA')what,
COALESCE(P.what,'NA')what,
ROW_NUMBER()OVER(partition by R.identifier,r.category ORDER by (select null))RN
from reports R left join status S
ON S.identifier = R.identifier
LEFT JOIN Priority P
ON P.identifier = s.identifier
GROUP BY R.identifier,r.category,S.what,P.what)T
Where T.RN = 1
ORDER BY T.identifier