query problem with many-to-many

Mika · **Joined:** Fri Mar 26, 2004 12:05 pm **Posts:** 3

I have the following query problem:

Class Base has a Set that holds references to objects of type D. This relationship is modeled as one-to-many.
Further on class Base has a Set with objects C (one-to-many) and C has two Sets that hold also references to objects of type D. The two D-Sets of C are modeled as many-to-many.

Therefore the associations between the objects is of this kind:

Code:

      |->D
Base->C
 |    |->D
 |->D

Now I want to create a HQL-Query that queries the D. Is it possible when starting from Base-object to query the D from Base->D and also the D from C->D in one HQL-Query?

Many thanks,

Mika

emmanuel · **Posted:** Thu May 06, 2004 6:13 am

union is not possible
But you can return a cartesian product select d1, d2, d3 from ... I don't think it'll fit your needs

Mika · **Joined:** Fri Mar 26, 2004 12:05 pm **Posts:** 3

thanks for the reply!

I added a many-to-one association from D to Base in the D-Mapping and selects the D by this query

Code:

select d from Base as b, D as d where d.base = b

Tests show that it works, but is this recommended? Besides the association between Base->D the Base and D have no direct association but an indirect association over C.

Many thanks,

Mika

emmanuel · **Posted:** Thu May 06, 2004 11:14 am

Code:

select d from Base as b join b.cs as c join c.ds where d.base = b

Will not break you relational model