Select Newest Record - sql-server

Question

I have two tables (Journal and Incident). Each incident may have more than one journal entry. I want to select the record and the most recent journal data.
The where section at the bottom is what filters the incidents I want to see. Of those, I want the journal values associated with the most recent journal entry.
This is an amalgam of code I've found on here, but when I run it I get a "Query execution failed for dataset 'DataSet1'. Unfortunately, I don't have access to the log files to see if there are clues there.
Any help is appreciated. I think I may have it nested wrong.
SELECT
b.IncidentNumber
,a.Subject
,a.CreatedDateTime
,b.SubCategory
,b.EffectiveDueDate
,b.NextActionDate
,b.ProfileFullName
FROM
(
SELECT
b.IncidentNumber
,a.Subject
,a.CreatedDateTime
,rn = row_number() OVER (PARTITION by b.IncidentNumber ORDER BY
a.CreatedDateTime DESC)
,b.SubCategory
,b.EffectiveDate
,b.NextActionDate
,b.ProfileFullName
FROM
Journal a LEFT JOIN Incident b ON
a.ParentRecordNumber = b.IncidentNumber
WHERE a.Category LIKE '%KANBAN%'
AND (b.Status LIKE' %Waiting%' OR b.status LIKE '%Active%')
AND b.SubCategory <> 'User Termination'
AND b.SubCategory <> 'Res Temp Termination'
AND a.Subject LIKE 'UP |%'
) X
WHERE rn = 1

Answer 1

Few things:
Outer most selected values should be from inline view aliased "X" No a. or b. as those alias only are in scope to the in inner query. (except when using coorlation but that's 1 level only I believe)
You either need to right join instead of left or change the order of the tables. I believe you want all incidents and the MOST recent Journal; not all journals and the related incident if one exists. thus I changed the order.
Lastly when using outer joins, you can only put limits on the all records table of the outer join. Where clause criteria the OUTER joined tables will cause the null records generated by the outer join to be excluded. To resolve this you must move the limiting criteria to the join or use an 'or' statement to check for null (it's cleaner to move it to the join). Think of it is applying the limit before the join occurs so Null records from incident are kept. otherwise the outer join simulates a INNER JOIN by excluding those records not in both tables (or in this case in incident but not in journal)
.
SELECT x.IncidentNumber --alias x not a/b as the from is aliased as 'X'
, x.Subject
, x.CreatedDateTime
, x.SubCategory
, x.EffectiveDueDate
, x.NextActionDate
, x.ProfileFullName
FROM (SELECT b.IncidentNumber
, a.Subject
, a.CreatedDateTime
, rn = row_number() OVER (PARTITION by b.IncidentNumber
ORDER BY a.CreatedDateTime DESC)
, b.SubCategory
, b.EffectiveDate
, b.NextActionDate
, b.ProfileFullName
FROM Incident b --switched the order I think you want all incidents and if a journal exists it's value.
LEFT JOIN Journal a
ON a.ParentRecordNumber = b.IncidentNumber
-- Since A is on the if match found to B, we need to move this to the join or we lose the records created from the outer join.
AND a.Category LIKE '%KANBAN%'
AND a.Subject LIKE 'UP |%'
--moved some where clause criteria to the join Since B is on the "all records side" of the outer join we can leave B in the where clause.
WHERE (b.Status LIKE' %Waiting%' OR b.status LIKE '%Active%')
AND b.SubCategory <> 'User Termination'
AND b.SubCategory <> 'Res Temp Termination') X
WHERE rn = 1
If you are not getting records from here, then I'd start removing some of the limiting criteria to ensure the query is functioning as desired and then add back in limits to see what's causing no records to be found.

Answer 2

I've finally got this report working as expected. It took a few iterations to get the query working, but it's doing what it should, now. Many thanks for your assist. I would have never gotten there without it!
SELECT x.IncidentNumber
, x.Subject
, x.CreatedDateTime
, x.SubCategory
, x.ProfileFullName
, x.PropertyNumber
, x.Status
, x.EffectiveDueDate
FROM (SELECT b.IncidentNumber
, a.Subject
, a.CreatedDateTime
, rn = row_number() OVER (PARTITION by b.IncidentNumber
ORDER BY a.CreatedDateTime DESC)
, b.SubCategory
, b.ProfileFullName
, b.PropertyNumber
, b.Status
, b.EffectiveDueDate
FROM Incident b
RIGHT JOIN Journal a
ON a.ParentRecordNumber = b.IncidentNumber
AND a.Category LIKE '%KANBAN%'
AND a.Subject LIKE 'UP |%'
WHERE (b.Status LIKE' %Waiting%' OR b.status LIKE '%Active%')
) x
WHERE rn = 1