create table PROFILE (
    ID integer,
    NAME varchar(64) not null
);

alter table PROFILE add constraint IDX_PROFILE_ID primary key (ID);

create table FRIEND (
    FROM_ID integer not null,
    TO_ID integer not null
);

alter table FRIEND add constraint IDX_FRIENDS_IDS primary key (FROM_ID, TO_ID);
alter table FRIEND add constraint FK_FRIENDS_FROM_ID foreign key (FROM_ID) references PROFILE(ID);
alter table FRIEND add constraint FK_FRIENDS_TO_ID foreign key (TO_ID) references PROFILE(ID);

select P.NAME, exists(select * from FRIEND where FRIEND.FROM_ID = :ID and FRIEND.TO_ID = P.ID) as IS_FRIEND
from PROFILE as P
where P.ID != :ID;

public class SocialProfileData {
    private String name;
    private boolean isFriend;

//+ getters/setters
}

public class ProfileData {
    private int id;
    private String username;
    private Set<ProfileData> friends;

//+ getters/setters
}

A>select P.NAME, exists(select * from FRIEND where FRIEND.FROM_ID = :ID and FRIEND.TO_ID = P.ID) as IS_FRIEND
A>from PROFILE as P
A>where P.ID != :ID;
A>

A>public class SocialProfileData {
A>    private String name;
A>    private boolean isFriend;

A>//+ getters/setters
A>}
A>

SELECT NEW SocialProfileData(
    p.name, 
    CASE 
        WHEN EXISTS (SELECT q.id FROM profile q WHERE p MEMBER OF q.friends)) 
            THEN TRUE
        ELSE FALSE
    END
    )
FROM profile p
WHERE p.id = :id

BB>SELECT NEW SocialProfileData(
BB>    p.name, 
BB>    CASE 
BB>        WHEN EXISTS (SELECT q.id FROM profile q WHERE p MEMBER OF q.friends)) 
BB>            THEN TRUE
BB>        ELSE FALSE
BB>    END
BB>    )
BB>FROM profile p
BB>WHERE p.id = :id
BB>

public class ProfileData {
    private int id;
    private String username;
    private Set<ProfileData> referalFriends; // те, у кого этот пользователь в друзьях
    private Set<ProfileData> friends; // друзья этого пользователя
//...
}

кусок маппинга:

<entity name="ProfileData" class="domain.ProfileData">
    <table name="PROFILE_DATA"/>
    <attributes>
        <id name="id">
            <column name="ID"/>
            <generated-value strategy="TABLE"/>
        </id>
        <basic name="username">
            <column name="USERNAME" nullable="false" length="64"/>
        </basic>
        <many-to-many name="referalFriends" fetch="EAGER">
            <join-table name="FRIEND">
                <join-column name="TO_ID" referenced-column-name="ID"/>
                <inverse-join-column name="FROM_ID" referenced-column-name="ID"/>
            </join-table>
        </many-to-many>
        <many-to-many name="friends" fetch="EAGER" mapped-by="referalFriends"/>
    </attributes>
</entity>

SELECT NEW samples.model.SocialProfileData(
    p.name,
    CASE 
        WHEN EXISTS (SELECT q.id FROM Profile q WHERE q.id = :id AND p MEMBER OF q.friends) 
            THEN TRUE
        ELSE FALSE
    END
    )
FROM Profile p
WHERE p.id <> :id