Why is ORM considered good but “select *” considered bad?

Question

Doesn\'t an ORM usually involve doing something like a select *?

If I have a table, MyThing, with column A, B, C, D, etc, then there typically would be an object, MyThin

Answer 1

I am not sure why you would want a partially hydrated object. Given a class of Customer with properties of Name, Address, Id. I would want them all to create a fully populated Customer object.

The list hanging off of Customers called Orders can be lazily loaded when accessed though most ORMs. And NHibernate anyway allows you to do projections into other objects. So if you had say a simply customer list where you displayed the ID and Name, you can create an object of type CustomerListDisplay and project your HQL query into that object set and only obtain the columns you need from the database.

Friends don't let friends premature optimize. Fully hydrate your object, lazy load it's associations. And then profile your application looking for problems and optimize the problem areas.