SOQL Childrecord-rollup for PersonAccounts

Question

What is the best way to get the number of childrecords on a personaccount with the PersonContactId as Id field, the lookup being a contact lookup?

I have the object Newsletter, with a contact lookup field and want a SOQL which gives me personaccounts with the number of related newsletter.

I tried: [SELECT ID, PersonContactId, (SELECT Id FROM Newsletter__r) FROM Account], but it only tells me that it doesnt understand the relationship.

I also tried getting the it with a separate SOQL: [SELECT Id, count(Id) FROM Newsletter__c WHERE ContactId__c in :setPersonAccounts], but I get the error "Field must be grouped or aggregated: Id" and if I group by id I get the error "Grouped field should not be aggregated: Id".

Answer 1

You can use like that .just used Newsletter__r( child relationship name )

List AccountList = [SELECT Name, (SELECT id FROM Newsletter__r) FROM Account]; for (Account Acc: AccountList ) { // do something with it... Acc.Newsletter__r.size(); }