NHibernate - Left joins - nhibernate

Question

I have the following two tables:
Jobs AreaID, JobNo (composite key)
Logs LogID, AreaID, JobNo
I need to get all jobs that don't have any logs associated with them. In SQL I could do:
SELECT Jobs.AreaID,
Jobs.JobNo
FROM Jobs
LEFT JOIN Logs
ON Jobs.AreaID = Logs.AreaID
AND Jobs.JobNo = Logs.JobNo
WHERE Logs.LogID is null
But I'm not sure how to accomplish this with NHibernate. Could anyone offer any pointers?
Here are my mappings:
<class name="Job" table="Jobs">
<composite-key name="Id">
<key-property name="JobNo"/>
<key-many-to-one name="Area" class="Area" column="AreaID"/>
</composite-key>
</class>
<class name="Log" table="Logs">
<id name="Id" column="LogID">
<generator class="identity"/>
</id>
<property name="JobNo"/>
<many-to-one name="Area" class="Area" column="AreaID"/>
</class>
Thanks
Update
OK, I modified Nosila's answer slightly, and this is now doing what I wanted:
Log logs = null;
return session.QueryOver<Job>()
.Left.JoinAlias(x => x.Logs, () => logs)
.Where(x => logs.Id == null)
.List<Job>();
I also had to add this to my Job mapping:
<bag name="Logs">
<key>
<column name="JobNo"></column>
<column name="DivisionID"></column>
</key>
<one-to-many class="Log"/>
</bag>
Thanks for the help. :)

Answer 1

I'm not familiar with composite identifiers as I don't use them so for all I know NHibernate will automatically create the proper left join. None the less, the (non-tested) query below should get you started.
Job jobAlias = null;
Log logAlias = null;
YourDto yourDto = null;
session.QueryOver<Job>()
// Here is where we set what columns we want to project (e.g. select)
.SelectList(x => x
.Select(x => x.AreaID).WithAlias(() => jobAlias.AreaID)
.Select(x => x.JobNo).WithAlias(() => jobAlias.JobNo)
)
.Left.JoinAlias(x => x.Logs, () => logAlias, x.JobNo == logAlias.JobNo)
.Where(() => logAlias.LogID == null)
// This is where NHibernate will transform what you have in your `SelectList()` to a list of objects
.TransformUsing(Transformers.AliasToBean<YourDto>())
.List<YourDto>();
public class YourDto
{
public int AreaID { get; set; }
public int JobNo { get; set; }
}
Note: You need NHibernate 3.2 in order to set join conditions.

Answer 2

Job job = null;
var jobsWithoutLogs = session.QueryOver(() => job)
.WithSubquery.WhereNotExists(QueryOver.Of<Log>()
.Where(log => log.Job == job)
.Select(Projections.Id()))
.List()
Update: i saw you added the mapping. The Above Code only works for the following mapping
<class name="Log" table="Logs">
<id name="Id" column="LogID">
<generator class="identity"/>
</id>
<many-to-one name="Job" >
<column name="JobNo"/>
<column name="AreaID"/>
<many-to-one />
</class>