querying all related records of a parent dynamically

Question

How to query dynamically all the related records or child of a parent using parentid If you take for Account , Case,Partners,Opportunity,Note & Attachments etc...

Answer 1

Suppose you have an Id in a variable recordId.

First fetch a map of keyPrefixes to its related SObjectType,

Map<String,Schema.SobjectType> keys = new Map<String,Schema.SobjectType>();
Map<String,Schema.SobjectType> describe = Schema.getGlobalDescribe();
for(String s:describe.keyset())
    keys.put(describe.get(s).getDescribe().getKeyPrefix(),describe.get(s));

Next, use your recordId to fetch the correct SObjectType and then fetch it's all children SObjectTypes.

Schema.SObjectType sobjectTypeObj = keys.get(recordId.substring(0,3));

Schema.DescribeSObjectResult obj = sobjectTypeObj.getDescribe();
for (Schema.ChildRelationship cr: obj.getChildRelationships()) 
{
  system.debug('Child Object Name:'+cr.getChildSObject());
}

Once you have all the child names, its pretty easy to for a nested SOQL of parent and child objects, like Select Id, Name, (Select Id, Name from Contacts) from Account

Answer 2

You can query the related objects to the Account like this:

select (select Id from Cases),(select Id from Opportunities),(select Id from Notes),(select Id from Attachments) from Account

Answer 3

The DescribeSObjectResult Class should help you here:

Schema.DescribeSObjectResult describe = Account.sObjectType.getDescribe();

for (Schema.ChildRelationship child : describe.getChildRelationships()){

//do your logic

}

Answer 4

If you want to retrieve all parents you need to use the describe the ParentId field.

    Schema.DescribeFieldResult f = Schema.sObjectType.Attachment.fields.parentid;
System.debug('Relationship Name: ' + f.getRelationshipName());    

for(Schema.SObjectType reference : f.getReferenceTo()) {
    System.debug('Lookup reference object name: ' + reference.getDescribe().getName());
    System.debug('Lookup reference object label: ' + reference.getDescribe().getLabel());
}

Code segment that you can use all the objects where it is referenced and then you create a dynamic SOQL. which can be used in Database.Query();

The answers is lited here.

Let me know if it resolves.