I have a query and I need to do a subQuery on it, I have tryed everything but I don't find the way to make it work.

select id, 
    (Select id, name, Childfield__c
        from ChildObject__c)

    from ParentObject__c
    where ParentObject__c = :varToFilter

The error is:

Didn't understand relationship 'ChildObject__c' in FROM part of query call. If you are attempting to use a custom relationship, be sure to append the '__r' after the custom relationship name. Please reference your WSDL or the describe call for the appropriate names.

What should I do to make it work.

1 Answer 1


Typically, the relationship is plural, and a custom relationship will alway end in __r. Try:

(SELECT Name FROM ChildObjects__r)

You can always get the verbatim name via this Execute Anonymous script:

for (ChildRelationship relation : SObjectType.ParentObject__c.getChildRelationships())
    if (relation.getChildSObject()() == ChildObject.sObjectType)

Whatever this script spits out, put in place of ChildObjects__r.

  • 1
    A child relationship name ends in __r in most situations, but not in all situations (i.e. not for standard relationships). Consider [SELECT Id, (SELECT Id FROM Opportunities) FROM Account].
    – Derek F
    Commented Feb 9, 2017 at 19:35
  • I personally feel the easy way to get child relationship names is via workbench.
    – javanoob
    Commented Feb 9, 2017 at 20:29
  • It's another route. You can get the describes however you wish, but the point is that's where you need to look. Workbench requires a separate login so usually I don't go that route (especially since I normally have the Dev Console open anyway).
    – Adrian Larson
    Commented Feb 9, 2017 at 20:30

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