Perhaps this?
USE [test]
go
select
ComponentId,
partRefId = MIN(partRefId),
Name,
DocumentId,
SheetRef = MIN(SheetRef),
LocationId,
Effectivity,
EffectivityId,
DesignatorPrefix,
Designator,
DesignatorSuffix
FROM PartRef pr
JOIN PartDef pd
ON pd.PartDefId = pr.PartDefId
Where pd.PartClass = 'Component' AND pr.EffectivityId = '11'
group by
ComponentId,
Name,
DocumentId,
LocationId,
Effectivity,
EffectivityId,
DesignatorPrefix,
Designator,
DesignatorSuffix