When creating records and relating them using foreign key is there a way to make this non critical, Take an example from http://bobbuzzard.blogspot.co.uk/2012/03/create-parent-and-child-records-in-one.html
Account acc=new Account(Name='Blog Acc 8', Master_Id__c='Blog Acc 8');
Contact cont=new Contact(FirstName='Bob', LastName='Buzzard', Account=new Account(Master_Id__c='Blog Acc 8'));
insert new List<Sobject>{acc, cont};
This would create both the Account and Contact and relate them together.
...suppose the Account already existed so we were just creating a Contact...
Contact cont=new Contact(FirstName='Bob', LastName='Buzzard', Account=new Account(Master_Id__c='Blog Acc 8'));
insert cont;
...now lets assume we did this but the Account didn't exists, as standard if the FK relationship does not exist an "INVALID_FIELD" exception is thrown:
INVALID_FIELD, Foreign key external ID: Blog Acc 8 not found
Can this constraint be disabled so the Contact record would be created without the relationship?