I've got a nasty problem and no idea how to solve this.

First: This is a legacy database, which i cannot change :-(

I have 2 entities Drvor and Vdrau both with the same compound key. Vdrau contains additional information, but only if the column DVABNR is >1500

With this solution it works (i had to add the @NotFound annotation, see below), but not optimal. It generates a seperate sql call for every row that has no data in Vdrau.

I looked at the @WhereJoinTable annotation, but it doesn't work with @MayToOne :-(

@Entity
public class Drvor implements Serializable {
 @EmbeddedId
 private DrvorPK pk = new DrvorPK();

 @ManyToOne(fetch = FetchType.LAZY)
 @Fetch(FetchMode.JOIN)
 @JoinColumns({
 @JoinColumn(name="DVAUN1", insertable=false, updatable=false),
 @JoinColumn(name="DVAUN2", insertable=false, updatable=false),
 @JoinColumn(name="DVAUJJ", insertable=false, updatable=false),
 @JoinColumn(name="DVABNR", insertable=false, updatable=false)
 })
 @NotFound(action=NotFoundAction.IGNORE)
 public Vdrau vdrau;
 ...
}