Selecting rows with highest date - sql

Question

I have the following query that throws a result like in the example:
SELECT P.IdArt, P.IdAdr, P.gDate, P.Price
FROM dbo.T_PriceData AS P INNER JOIN
dbo.T_Adr AS A ON P.IdAdr = A.IdAdr INNER JOIN
dbo.T_Stat AS S ON A.IdStat = S.IdStat
GROUP BY P.IdArt, P.IdAdr, P.gDate, P.Price
IdArt IdAdr gDate Price
1 10 01/01/2018 1.25
1 10 02/01/2018 1.17
1 10 03/01/2018 1.18
2 15 01/01/2018 1.03
2 18 10/01/2018 0.12
3 25 12/01/2018 0.98
3 25 28/01/2018 1.99
4 30 15/01/2018 2.55
5 35 08/01/2018 0.11
The final result I want is:
When the IdArt and IdAdr are the same, there should be only one row with the highest date of all rows (CASE IdArt 1)
When IdArt is the same but IdAdr is different, there should be a row with each IdAdr with the highest date for each IdAdr. (CASE IdArt 2)
Price doens't affect anything.
So the final table I would like to have is:
IdArt IdAdr gDate Price
1 10 03/01/2018 1.18
2 15 01/01/2018 1.03
2 18 10/01/2018 0.12
3 25 28/01/2018 1.99
4 30 15/01/2018 2.55
5 35 08/01/2018 0.11
How can I do that?
I tried with a having clausule selecting by MAX(gDate) but, of course, I only get one row with the max date from the whole database.

Answer 1

There are lots of answers out there on how to do this, however, this gets you what you are after:
SELECT TOP 1 WITH TIES
P.IdArt,
P.IdAdr,
P.gDate,
P.Price
FROM dbo.T_PriceData P
--INNER JOIN dbo.T_Adr A ON P.IdAdr = A.IdAdr --You don't reference this in the SELECT or WHERE. Why is it here?
--INNER JOIN dbo.T_Stat S ON A.IdStat = S.IdStat --You don't reference this in the SELECT or WHERE. Why is it here?
ORDER BY ROW_NUMBER() OVER (PARTITION BY P.IdArt, P.IdAdr ORDER BY P.gDate DESC);
Edit: If the JOINs are there to ensure that there are rows in the other tables, then as per the comments I would use EXISTS. If you just use JOIN, and only returning rows from the first table, then you could end up with duplicate rows.
SELECT TOP 1 WITH TIES
P.IdArt,
P.IdAdr,
P.gDate,
P.Price
FROM dbo.T_PriceData P
WHERE EXISTS (SELECT 1
FROM dbo.T_Adr A
WHERE P.IdAdr = A.IdAdr)
AND EXISTS (SELECT 1
FROM dbo.T_Stat S
WHERE A.IdStat = S.IdStat)
ORDER BY ROW_NUMBER() OVER (PARTITION BY P.IdArt, P.IdAdr ORDER BY P.gDate DESC);

Answer 2

You want the highest date for each IdArt/IdAdr combination. Window functions are tempting, but the most efficient method is often a correlated subquery.
Your query is only selecting from T_PriceData, so the rest of the query (the joins and group by) do not seem necessary -- unless the joins are filtering the data which seems unlikely because the joins are to reference tables.
So I would recommend:
SELECT P.IdArt, P.IdAdr, P.gDate, P.Price
FROM dbo.T_PriceData P
WHERE P.gDate = (SELECT MAX(P2.gDate)
FROM dbo.T_PriceData P2
WHERE P2.IdArt = P.IdArt AND
P2.IAdr = P.IdAdr
);
For performance you want indexes on (IdArt, IdAdr, gDate).

Answer 3

You can use ROW_Number():
SELECT
q.IdArt
, q.IdArt
, q.IdADr
, q.gDate
, q.Price
FROM (
SELECT
t.IdArt
, t.IdADr
, t.gDate
, t.Price
, ROW_NUMBER() OVER (PARTITION BY t.IdArt, t.IdADr ORDER BY t.gDate DESC) rn
FROM dbo.T_PriceData t
) q
WHERE q.rn = 1