Question

I have several objects classes mapped to a database using annotations and need some help working out how to put together a Hibernate query to get the results I want.

I’m using Hibernate 3.6.5. I’ve been using Criteria, but happy with Query etc if it works!

I’m new to Hibernate (can manage simple Criteria to filter objects by property but the join stuff is all new), so any explanation in the answer (or suggested reading) would be great.

A RawRead has a tagcode field which contains a String.
Checkpoint, IncidentItem and Guard classes all also have a TagCode property.

I want to retrieve all RawRead objects where the TagCode doesn’t match any tagcode value from any of the other classes (IncidentItem, Guard, Checkpoint).

A sort of brain dump/psuedo SQL code:

select raw.* from 
    RAWREADS raw, checkpoints c, GUARDS g, INCIDENTITEMS i 
    where 
    raw.tagcode != c.TAGNO
    and raw.TAGCODE != g.IDTAG
    and raw.TAGCODE != i.IDTAG;

I realise that won’t be efficient etc, just an illustration of my thoughts.

Can you suggest what to look at in Hibernate language?

EDIT/Additions:
The RawRead object is mapped to Guard and Checkpoint (has a property called checkpoint and one called guard that are both instances of those classes – both are @ManyToOne).

IncidentItem does not have any mapping to the other classes.

Answer 1

In order to join objects in HQL there has to be a relationship mapped between them in the annotations at the application level. If there are no mapped relationships, you’ll need to do a query like this in plain SQL.