Hi,

We are working with a legacy framework that permits us to manipulate DB schema to a degree, but the incoming data relationships and the outgoing data relationships are generally fixed. Basically, I'd like to express a simple inner join in my mappings like this:



So the above is what I am really interested in representing in my mappings. The actual mappings I'm using are as follows:




My goal is to express joins in my mappings so that a query on tier2 pulls the description from tier1 and a query on tier3 pulls the description from tier1 and tier2.

If this is too complex for a mapping (ie. it is not within the conceptual scope of Hibernate's mapping framework), I may be forced to resort to direct HQL queries ... but it would be nice to represent these things as objects in a mapping, because then I get that DB -> XML/object relationship. :)

I am not clear what exactly you want to do. If you solution in terms of mapping only, then create a view in database which has same columns and data which you want. Now in mapping file you can map this view to your class.

Yeah -- thanks for the suggestion -- I actually thought about the view option, but was curious if it could be expressed within the mapping itself.

Playing around with these mappings this morning, I realized that I hadn't really set up the class relationships correctly. A revised set of mappings:



The above is a more accurate representation of the relationship between tier1, tier2 and tier3. So the first problem is the join issue, where I wanted a nice way to express the join in the mapping. The <many-to-one> references in tier2 and tier3 sort of achieve this, in that I can now access the information I need through the many-to-one relationship. I could alternatively modify the classes slightly to support views for tier2 and tier3, which would also work.

However, now that I am using composite-id's, I no longer have my nice identity column "id" expressed as a <generator>. I still need that identity column, so it is now represented as a <property>, but I do not seem to have a way of expressing (in a mapping) that it is an identity column, but not a primary key.

Right now, I am generating the tables using SQL, where the "id" column is created as:

but I do not see a way of expressing this in a mapping when "id" is not a primary key on the table.


Any suggestions are welcome.