Window function issue - max over partition - sql

Question

I try to rewrite such SQL statements (with many subqueries) to more efficient form using outer join and max/count/... over partition. Old statements:
select a.ID,
(select max(b.valA) from something b where a.ID = b.ID_T and b.status != 0),
(select max(b.valB) from something b where a.ID = b.ID_T and b.status != 0),
(select max(b.valC) from something b where a.ID = b.ID_T and b.status != 0),
(select max(b.valD) from something b where a.ID = b.ID_T)
from tool a;
What is important here - there is different condition for max(b.valD). Firstly I didn't noticed this difference and write something like this:
select distinct a.ID,
max(b.valA) over (partition by b.ID_T),
max(b.valB) over (partition by b.ID_T),
max(b.valC) over (partition by b.ID_T),
max(b.valD) over (partition by b.ID_T),
from tool a,
(select * from something
where status != 0) b
where a.ID = b.ID_T(+);
Could I use somewhere in max over partition this condition of b.status != 0 ? Or should I better add 3rd table to join like this:
select distinct a.ID,
max(b.valA) over (partition by b.ID_T),
max(b.valB) over (partition by b.ID_T),
max(b.valC) over (partition by b.ID_T),
max(c.valD) over (partition by c.ID_T),
from tool a,
(select * from something
where status != 0) b,
something c
where a.ID = b.ID_T(+)
and a.ID = c.ID_T(+);
The issue is with selecting and joining millions of rows, my example is just simplification of my query. Could anyone help me to achieve more efficient sql?

Answer 1

You could try to do this using CASE:
select a.ID,
max(CASE WHEN b.status=0 THEN b.valA END),
max(CASE WHEN b.status=0 THEN b.valB END),
max(CASE WHEN b.status=0 THEN b.valC END),
max(b.valD)
from tool a
left join something b ON( b.ID_T = a.ID )
group by a.ID;
Note that I replaced your implicit join by the "new" join-syntax for better readability.

Answer 2

One more way is to use JOIN and group by subquery:
select a.ID,
b.MAX_A,
b.MAX_B,
b.MAX_C,
b2.MAX_D
from tool a
LEFT JOIN
(
SELECT ID_T,max(valA) MAX_A, max(valB) MAX_B, max(valC) MAX_C
FROM something
WHERE status != 0
GROUP BY ID_T
) b
ON a.ID=b.ID_T
LEFT JOIN
(
SELECT ID_T, max(valD) MAX_D
FROM something
GROUP BY ID_T
) b2
ON a.ID=b2.ID_T