SQL Server 2012, only show one row if other exists - sql-server

Question

Question:
I get these results (column task_externalId) when I run my query:
TC229090-10000-3
TC229090-20000-3
TC229830-10000-3
TC229685-10000-3
A task (TC229090) can contain multiple rows (10000, 20000), but can also have just one (10000 only).
My full code:
SELECT
v.voorgemeld_handmatig, v.voorgemeld, v.mac, v.orn, v.cdm, v.blo,
v.bco, v.tarcode, (v.timeslotfrom + ' - ' + v.timeslottill),
cast (case
when
(Select ac2.actionSpecificationName
From [COMTECdefault].[dbo].[task] t2
Join [COMTECdefault].[dbo].[actionKind] ak2 On t2.id_actionKind = ak2.id_actionKind
Join [COMTECdefault].[dbo].[actionSpecification] ac2 On ak2.id_actionSpecification = ac2.id_actionSpecification
where t2.task_externalId = (left(t.task_externalId, 15) + '2')) = 'laden'
then 'Vol'
else 'Leeg'
end as text) as IMPORT,
t.task_externalId, a.addressName, a.cityName,
CONVERT(DATE, t.from_date) as [Date],
CONVERT(varchar(8), CONVERT(TIME, t.from_date)) as [Tijd],
res.resourceName, resk.resourceKindName, r.shipOwner,
t.reference,
(Select resourceName
From [COMTECdefault].[dbo].[resource] r5
Left Outer Join [COMTECdefault].[dbo].resourceKind rk5 On rk5.id_resourceKind = r5.id_resourceKind
Where (id_resource = SUBSTRING(pt.StartResources, 0, CHARINDEX(',', pt.StartResources))
or id_resource = PARSENAME(REPLACE(SUBSTRING(pt.StartResources, CHARINDEX(',', pt.StartResources) + 1, LEN(pt.StartResources)), ',', '.'), 4)
or id_resource = PARSENAME(REPLACE(SUBSTRING(pt.StartResources, CHARINDEX(',', pt.StartResources) + 1, LEN(pt.StartResources)), ',', '.'), 3)
or id_resource = PARSENAME(REPLACE(SUBSTRING(pt.StartResources, CHARINDEX(',', pt.StartResources) + 1, LEN(pt.StartResources)), ',', '.'), 2)
or id_resource = PARSENAME(REPLACE(SUBSTRING(pt.StartResources, CHARINDEX(',', pt.StartResources) + 1, LEN(pt.StartResources)), ',', '.'), 1))
and r5.id_resourceKind = 51),
udo.udf_Gewicht, udo.udf_Zegelnummer,
cast (case when a.addressName = 'APM Terminal 2'
then case when udo.udf_Zegelnummer IS NULL
then 0
else 1
end
when a.addressName IN ('ect delta', 'Euromax Terminam C.V.', 'Euromax Terminal')
then case when udo.udf_Gewicht = 0
then 0
else 1
end
else 1
end as bit) as [voormelden],
v.foutcode, v.foutcode_tekst, v.V_door
FROM
[COMTECdefault].[dbo].[task] t
JOIN
[COMTECdefault].[dbo].[actionKind] ak ON t.id_actionKind = ak.id_actionKind
JOIN
[COMTECdefault].[dbo].[actionSpecification] ac ON ak.id_actionSpecification = ac.id_actionSpecification
LEFT OUTER JOIN
[COMTECdefault].[dbo].[resourceOrder] ro ON t.id_order = ro.id_order
LEFT OUTER JOIN
[COMTECdefault].[dbo].[resource] res ON ro.id_resource = res.id_resource
LEFT OUTER JOIN
[COMTECdefault].[dbo].[resourceKind] resk ON res.id_resourceKind= resk.id_resourceKind
LEFT OUTER JOIN
[COMTECdefault].[dbo].[address] a ON t.id_address = a.id_address
LEFT OUTER JOIN
[COMTECdefault].[dbo].[resourceOrder] r ON t.id_order = r.id_order
LEFT OUTER JOIN
[COMTECdefault].[dbo].[order] o ON o.id_order = r.id_order
LEFT OUTER JOIN
[COMTECdefault].[dbo].[voormelden] v ON v.id_task_otd = t.task_externalId
LEFT OUTER JOIN
[COMTECdefault].[dbo].[ud_order] udo ON udo.id_order = t.id_order
LEFT OUTER JOIN
[COMTECdefault].[dbo].[plannedTask] pt on t.id_task = pt.id_task
WHERE
(pt.id_Task IS NULL OR pt.taskstate <> 'finished')
AND (v.canceled IS NULL OR v.canceled = 0)
AND left(res.resourceName, 4) <> 'XXXU'
AND t.canceled = 0
AND (t.from_date <= '2016-11-24 23:59:59')
AND (ac.actionSpecificationName = 'inleveren')
AND a.addressName IN ('APM Terminal 1','APM Terminal 2', 'ect delta', 'rwg', 'Euromax Terminam C.V.', 'Euromax Terminal')
ORDER BY
res.resourceName, a.addressName, t.task_externalId
I only want to show the 20000 task when its exists . Otherwise show the 10000.
Thanks in advance.

Answer 1

I am not going to touch all of that text there may well be was of narrowing down all of the joins etc, but here is the pattern for doing what you want with the task_exteralid column.
DECLARE #Table AS TABLE (task_externalid VARCHAR(100))
INSERT INTO #Table VALUES
('TC229090-10000-3')
,('TC229090-20000-3')
,('TC229830-10000-3')
,('TC229685-10000-3')
;WITH cte AS (
SELECT
*
,RowNumber = ROW_NUMBER() OVER (PARTITION BY
LEFT(task_externalid,CHARINDEX('-',task_externalid) - 1)
ORDER BY task_externalid DESC)
FROM
#Table
)
SELECT *
FROM
cte
WHERE
RowNumber = 1
Create a partitioned ROW_NUMBER on the LEFT most portion of the task_exteralid
Order that by task_exteralid DESC