Named query, primary keys must not contain null

Question

We have an question on the named query. Here is the scenario:
Class JoinClassC (id, name, desc, comment) is mapped to two tables Join_Table_A (id, name, description) and Join_Table_B (id, name, comments); Join_Table_A is the primary table; two tables are associated via primary key.
Defined a named query (findByName, ReadAllQuery/SQL) for JoinClassC descriptor. The sql is:
SELECT a.ID,a.NAME,a.DESCRIPTION,b.COMMENTS FROM JOIN_TABLE_A a, JOIN_TABLE_B b WHERE a.NAME=#name AND a.ID=b.ID AND a.NAME=b.NAME
Getting QueryException while executing the query. Here is the trace:
[3/2/05 13:50:24:795 EST] f8b62aa SystemOut O 2005.03.02 01:50:24.795--ServerSession(738697921)--Thread[Servlet.Engine.Transports : 4,5,main]--Connection(1095574161)--SELECT a.ID,a.NAME,a.DESCRIPTION,b.COMMENTS FROM JOIN_TABLE_A a, JOIN_TABLE_B b WHERE a.NAME='persistence' AND a.ID=b.ID AND a.NAME=b.NAME
2005.03.02 01:50:24.835--ClientSession(1127670417)--Thread[Servlet.Engine.Transports : 4,5,main]--Exception [TOPLINK-6044] (OracleAS TopLink - 10g (9.0.4.4) (Build 040627)): oracle.toplink.exceptions.QueryException
Exception Description: The primary key read from the row [DatabaseRow(
     USER04.JOIN_TABLE_B.ID => 2
     USER04.JOIN_TABLE_A.NAME => persistence
     USER04.JOIN_TABLE_A.DESCRIPTION => FJF Persistence Fram
     USER04.JOIN_TABLE_B.COMMENTS => The Persistence Fram)] during the execution of the query was detected to be null. Primary keys must not contain null.
Query: ReadAllQuery(com.ford.it.persistence.unittest.dom.JoinClassC)Local Exception Stack:
Exception [TOPLINK-6044] (OracleAS TopLink - 10g (9.0.4.4) (Build 040627)): oracle.toplink.exceptions.QueryException
Exception Description: The primary key read from the row [DatabaseRow(
     USER04.JOIN_TABLE_B.ID => 2
     USER04.JOIN_TABLE_A.NAME => persistence
     USER04.JOIN_TABLE_A.DESCRIPTION => FJF Persistence Fram
     USER04.JOIN_TABLE_B.COMMENTS => The Persistence Fram)] during the execution of the query was detected to be null. Primary keys must not contain null.
Query: ReadAllQuery(com.ford.it.persistence.unittest.dom.JoinClassC)
     at oracle.toplink.exceptions.QueryException.nullPrimaryKeyInBuildingObject(QueryException.java:542)
Adding b.ID to the sql select will solve the problem.
Question: does the primary key must be present in the sql select to run this kind of query? Any way to work around the restriction?
Your help would be greatly appreciated.
Haiwei

Answer 1

The problem is that you need to select both primary keys for the multiple table descriptor.
i.e.
SELECT a.ID,a.NAME,a.DESCRIPTION,b.ID, b.COMMENTS FROM JOIN_TABLE_A a, JOIN_TABLE_B b WHERE a.NAME=#name AND a.ID=b.ID AND a.NAME=b.NAME
Your SQL needs to return the same data that TopLink would have selected, which includes the primary key for both tables. TopLink expects both a.ID and b.ID fields in the select, because your only select one and the field names are the same TopLink thought the ID field was for b.ID not a.ID, if you select both it will be ok.