Hibernate version: 3.1

Hi
Anybody know why I can't do this with hql?
(I know the given query is pointless, but it's a generic example of my real one)


It give me error like


The behavior I would expect from that query is for it to group by the class's mapped identifier and return the objects.

The following does not error, but is not what I want as it returns only id, not object


The following snippet from the documenation gives me the impression that I should be retrieve object grouped by object.


Please help.
Thanks you

try the following:
from MyClass obj group by obj.id

Thank you for suggestion. But I have already tried that and it give me same error. Does a query like that work for you? If so, I wonder if it because different database. I use sql 2000.

Does this work for anybody?

It really important for me.

Even if I did,

it seem like there could be a way to retrieve object instead of only id. Something like,

If you don't specify a select, than it will alyways load the objects.



Also this is already grouped by Object, because all objects are unique.

You only need and can specify a group by object when you use an aggregation on a relation of object.
i.e.:

momania, thank for reply. But, if you read my original post, it say this is only a simplified query (I know it is not useful by itself) that represents the problem. The real query is much more complex, but if you look at this example from the documentation you see that they are doing something similar. The object is in the select list (non-aggregated) and is also grouped. Does this work for anyone?

There is a aggregation, but it's in the order by.
That's what I was trying to explain you. As long as you don't use a join, aggregation, etc., you can not use the group by because it has no use. ;)

Maybe if you show us you more complex query, we can help you out with it ;)

What is expected result of this query ? "select cat from Cat cat group by cat"

Thank you both for trying help.



I would expect the exact same as what you get from "select cat from Cat cat".



Ok, I'll try another example. If I showed original, it would take 3 pages to explain ;)

Objective:
Return all unique combinations of Cat and Girlfriend along with a count of how many toys are shared between the girlfriends and the kittens (for each Cat/Girlfriend combo).


This works:




This one gives sql error:



From my perspective, if the first one should work, then the second one should work as well. I try to do the second one, because I don't want just the object id's, I want the actual object. But Hibernate try to group on all of the class's columns which doesn't correlate to anything in the select list, so it fails.
I got the impression that my query should work because of the example I pointed out from the documentation. I still don't understand what is so different about mine.

I have worked around it for now by using native sql query. But I would still like to understand as I'm sure it will come up for me again.

thanks you

Probably there is a mistake in example.
BTW it doe's not make sence to "group" if key is included (object always includes key) result will have no groups anyway, "group" makes sence for projection queries only.

Well essentially what I'm trying to do is something like "select distinct(a,b)". Since that is not legal, my understanding is to do it like "group by a,b". That gives me the results I'm looking for. Is there a better way?

It is better to filter records using "where", but if you can not find the right predicate then postprocess results on client using HashSet

BTW hibernate must not return duplicates from queries, it must be forced postprocess result by object identity management itself.

Ok.
Anyway, for another reference on what I was trying to accomplish. There is this link.

http://forum.hibernate.org/viewtopic.php?p=2273602&highlight=#2273602

Thanks again.

Is there any solution to this problem? It's a showstopper for us ...