The following is a HQL from chapter 14.14 of the reference documentation

If I want to have more order attributes along with the sum and count, how to modify this HQL? I think it should be something like

where the sum and count can be defined as @Transient attributes in the Order object. But, it won't work.

How to solve this problem?

Its not a good practice to pollute your domain objects with reporting attributes.
Better make a new pojo i.e. OrderSummary and introduce there properties for sums or counts together with whatever else you need. If your reporting changes you only need to modify those reporting classes.

Of course don't forget to import it to the hbm file where you define your hql

<import class="your.package.OrderSummary"/>

In my case, I already created a report domain object which is mapped into a view. It is read-only. Since a query in a view can't take any variables, I can't put any aggregation function in the view. I can get a list of those report objects first and iterate over the list to get those calculated data. I want to have a more effective approach, or a better/right solution for reporting.

I don't use any hbm XML mapping file any more, but annotation.

I don't know if this what you are looking for but here are my 2cents.
1)For the requirement of adding more attributes on Order object:-
Since the query uses group-by "order" object itself, have you tried in the projections as

Or

2)Resulting columns in a domain object.
if you succeed some how doing the Step 1, have you considered ResultSetTransformer to copy the data back to your Reporting POJO?

Hope this helps!

Thanks very much for your hint.

The first approach of the step 1 works, but not the second approach. Although I still need to walk over the returned list and put things together, it is far better than fetching data inside of the loop.

p.s. I need to create aliases for all returned data so that I can use Transformers.ALIAS_TO_ENTITY_MAP.