Using MAX for date but adding column to group on 'breaks' the query - sub query? - sql

Question

I Have a table which holds date but I need to know the latest date where a condition is true per location, only issue is once I add a column called 'notes' it breaks the query and returns too many rows, current query is ...
SELECT
Location,
MAX(date) AS date,
type,
notes
FROM NotesTable a
INNER JOIN Location b on a.LocationID = b.LocationID
INNER JOIN Type c on a.typeid = c.typeid
WHERE typeid <> 8
GROUP BY Location, type, notes
If I comment out the notes column then it works fine but as soon as I add that to the grouping it then returns more rows than required.
Have tried using a subquery but still cant get it working, subquery below
SELECT
r.location,
r.date,
r.type,
t.notes
FROM (SELECT Location, MAX(date), type
FROM NotesTable a INNER JOIN Location b on a.LocationID = b.LocationID
INNER JOIN Type c on a.typeid = c.typeid
WHERE typeid <> 8
GROUP BY location,type
) r
INNER JOIN NotesTable t ON t.date = r.date
Anyone got any other suggestions?

Answer 1

select * from
(
SELECT Location,Date, Type, Notes, Row_Number() Over (Partition By Location, Type order by date desc) RN
FROM
NotesTable a
INNER JOIN Location b on a.LocationID = b.LocationID
INNER JOIN Type c on a.typeid = c.typeid
WHERE typeid <> 8
) v
WHERE rn = 1

Answer 2

Your query is almost correct, you need to add this additional condition in ON clause
AND
t.location = r.location AND
t.type = r.type
full query,
SELECT r.location
, r.DATE
, r.type
, t.notes
FROM (
SELECT Location
, MAX(DATE) maxDate
, type
FROM NotesTable a
INNER JOIN Location b
ON a.LocationID = b.LocationID
INNER JOIN Type c
ON a.typeid = c.typeid
WHERE typeid <> 8
GROUP BY location
, type
) r
INNER JOIN NotesTable t
ON t.DATE = r.maxDate AND
t.location = r.location AND
t.type = r.type