как обновить запись, не беспокоясь о первичном ключе

+----------------------------------------------+-----------------------------------------------+
|                    list()                    |                   iterate()                   |
+----------------------------------------------+-----------------------------------------------+
| Return type is List                          | Return type is Iterate                        |
| All records loads at single database request | For each record, one database hit is made     |
| This is faster if cache is not available     | This is very slower if cache is not available |
| Eager loading                                | Lazy loading                                  |
+----------------------------------------------+-----------------------------------------------+  

Для списка ():

Query query = session.createQuery("from Employee");
List list = query.list(); // SELECT * FROM EMP
Iterator iterator = list.iterator();
while(iterator.hasNext()){
}  

Для итерации ():

Query query = session.createQuery("from Employee");
Iterator iterator = query.iterate(); // SELECT * FROM EMP
while(iterator.hasNext()){
    // SELECT * FROM EMP WHERE EMP_ID=?
}