hi
i have a class named Activity it has a many to many self relation
my annotation is as fallow:

@Entity
@Table(name = "Activity")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "type", discriminatorType = DiscriminatorType.STRING)
@javax.persistence.SequenceGenerator(
name = "SEQ_Activity",
sequenceName = "SEQ_Activity",
allocationSize = 1)

public class Activity implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_Activity")
@Column(name = "id")
private Long id;

@ManyToMany(targetEntity = Activity.class)
@JoinTable(name = "prerequisiteactivity",
joinColumns = {@JoinColumn(name = "act")},
inverseJoinColumns = {@JoinColumn(name = "pre")})
private Set<Activity> prerequisiteActivity = new HashSet<Activity>();

@ManyToMany(targetEntity = Activity.class, mappedBy = "prerequisiteActivity")
private Set<Activity> postRequisiteActivity = new HashSet<Activity>();
}

when i try to query my Activity class by ristriction on prerequisiteActivity & postRequisiteActivity
i get the "ORA-00918: column ambiguously defined" exception
the select statemnt generated by hibernate is like this

select * from (select
...
prerequisi60_.act as act,
activity33_.id as pre,
...
postrequis49_.pre as pre,
activity36_.id as act,
...
from from Activity this_ ...
inner join prerequisiteactivity prerequisi60_ on this_.id=prerequisi60_.act
inner join Activity activity33_ on prerequisi60_.pre=activity33_.id
inner join prerequisiteactivity postrequis49_ on this_.id=postrequis49_.pre
inner join Activity activity36_ on postrequis49_.act=activity36_.id
where ... ) where rownum <= ?