FATAL_ERROR|System.ListException: Row with null Id at index: 0

Question

I'm trying to query the Products that has more than 3 Quantity

Below is my query:

Set<Id> extras = new Map<Id, AggregateResult>([
    SELECT Product2Id
    FROM OpportunityLineItem
    WHERE Product2Id In: oppIds
    GROUP BY Product2Id
    HAVING SUM(quantity) > 3
]).keySet();

Any ideas on why I'm having

FATAL_ERROR|System.ListException: Row with null Id at index: 0

Answer 1

When using an AggregateResult query with the Map<Id, AggregateResult> constructor, you need to alias the field to the specific alias Id (case-sensitive):

Set<Id> extras = new Map<Id, AggregateResult>([
    SELECT Product2Id Id
    FROM OpportunityLineItem
    WHERE Product2Id In: oppIds
    GROUP BY Product2Id
    HAVING SUM(quantity) > 3
]).keySet();