One to Many Mapping with different SQL types

Question

We have an interesting one to many relationship in our system in which the source and target field SQL types do not match, but the values do. The relationship is actually between multiple entries in the same database table. So, imagine we have some table that looks sort of like this:
KEY ObjectID OwnerNo
100 1234     0
101 ABCD     1234
102 EFGH     1234ObjectID is defined as a varchar type, but Parent entries are guaranteed to have integer value ObjectIDs. Child entries point to the parent through the OwnerNo field, which defined in the database as a numeric.
A simple one-to-many mapping will give you the following SQL error on execution: [SQL0401] Comparison operator = operands not compatible.
I tried modifying my descriptor after load as follows:
   public static void modifyOneToMany(Descriptor descriptor)
       ExpressionBuilder builder = new ExpressionBuilder();
       Expression exp = builder.getField("OwnerNo").
          equal(builder.getField("ObjectID").toNumber());
       descriptor.getMappingForAttributeName("children")
          .setSelectionCriteria(exp);
   }But this introduces two problems in the generated SQL ( ... WHERE ((t0.OwnerNo = TO_NUMBER(t0.ObjectID) ... ). First, this generates a where clause using the function TO_NUMBER, which is not supported by DB2 on AS400, our database platform. Second, the table reference is off in the generated SQL--I couldn't find a way to specify that the right hand side of the = operator should be from the parent of the one to many mapping--both sides are referenced from the child context (t0).

Answer 1

I found the getFunction() method on Expression, so I can solve half of this problem with the following code:
   public static void modifyOneToMany(Descriptor descriptor)
     if (descriptor.getMappingForAttributeName("children").isOneToManyMapping())
       OneToManyMapping map = (OneToManyMapping) descriptor.
                              getMappingForAttributeName("children");
       DatabaseField objectID= (DatabaseField) map.getSourceKeyFields().get(0);
       DatabaseField ownerNo = (DatabaseField) map.getTargetForeignKeyFields().get(0);
       ExpressionBuilder builder = new ExpressionBuilder();
       Expression exp = builder.getField(ownerNo).getFunction("CHAR").
                        equal(builder.getField(objectID));
       map.setSelectionCriteria(exp);
   }This generates the following where clause:
... WHERE ((CHAR(t0.OwnerNo) = t0.ObjectID) ...
But, I still have two questions:
1. How do we get the right hand side of this comparison to reference the Parent part of the 1-M mapping?
2. Since character and numeric conversions are pretty standard SQL functions, is there something wrong with the DB2 database platform I'm using?