Conditional display of calculated fields - sql-server

Question

I'm working on a table named FCT_HISTO_PORTES that contains ID_MVT_EXPL and ID_PTE fields which are integers. In this table a ID_MVT_EXPL is associated with one, two or three ID_PTE.
Here's an example:
select top 1000
ID_MVT_EXPL,
ID_PTE
from FCT_HISTO_PORTES
ID_MVT_EXPL ID_PTE
3945546 6
3945547 25
3945548 56
3945548 57
3945549 25
3945550 52
3945551 57
3945551 58
3945553 56
3945557 51
3945558 57
3945558 58
You can see that "3945546" has one ID_PTE and "3945548" has two different ID_PTE.
The aim of the game is that I can display a single line for each ID_MVT_EXPL with named fields ID_PTE_1, ID_PTE_2, ID_PTE_3.
I tried with this SELECT but the result is incorrect because all the ID_PTE fit into ID_PTE_1 and leave the other two to NULL.
select top 1000
ID_MVT_EXPL,
MIN(id_pte) as ID_PTE_1,
case
when COUNT(id_pte) = 2
then MAX(id_pte)
when COUNT(id_pte) = 3
then SUM(id_pte)-(MIN(ID_PTE)+MAX(ID_PTE))
end as ID_PTE_2,
case
when COUNT(id_pte) = 3
then MAX(id_pte)
end as ID_PTE_3
from FCT_HISTO_PORTES
group by ID_MVT_EXPL, ID_PTE
ID_MVT_EXPL ID_PTE_1 ID_PTE_2 ID_PTE_3
3945546 6 NULL NULL
3945547 25 NULL NULL
3945548 56 NULL NULL
3945548 57 NULL NULL
3945549 25 NULL NULL
3945550 52 NULL NULL
3945551 57 NULL NULL
3945551 58 NULL NULL
3945553 56 NULL NULL
3945557 51 NULL NULL
3945558 57 NULL NULL
3945558 58 NULL NULL
So what needs to change in my SELECT?

Answer 1

My suggestion is a little bit different. But if I understand you correct. You could do this:
Test data:
DECLARE #tbl TABLE(ID_MVT_EXPL INT, ID_PTE INT)
INSERT INTO #tbl
VALUES
(3945546,6),(3945547,25),(3945548,56),(3945548,57),
(3945549,25),(3945550,52),(3945551,57),(3945551,58),
(3945553,56),(3945557,51),(3945558,57),(3945558,58)
Query:
SELECT
pvt.ID_MVT_EXPL,
pvt.[1] AS ID_PTE_1,
pvt.[2] AS ID_PTE_2,
pvt.[3] AS ID_PTE_3
FROM
(
SELECT
ROW_NUMBER() OVER(PARTITION BY tbl.ID_MVT_EXPL ORDER BY ID_PTE) AS RowNbr,
tbl.ID_MVT_EXPL,
tbl.ID_PTE
FROM
#tbl AS tbl
) AS SourceTable
PIVOT
(
MAX(ID_PTE)
FOR RowNbr IN([1],[2],[3])
) AS pvt
Output:
3945546 6 NULL NULL
3945547 25 NULL NULL
3945548 56 57 NULL
3945549 25 NULL NULL
3945550 52 NULL NULL
3945551 57 58 NULL
3945553 56 NULL NULL
3945557 51 NULL NULL
3945558 57 58 NULL
Reference:
ROW_NUMBER (Transact-SQL)
Using PIVOT and UNPIVOT