One-to-one behavior

[Anastasia-Tre]

I have query:

var query1 = _session.Query<MasterDetail>()
                      .Where(m => m.Master.Name.StartsWith("A"))
                      .ToList();

Nhibernate generates for the query sql:

select
  masterdeta0_.MasterDetailId as masterdetailid1_1_,
  masterdeta0_.Type as type2_1_ 
from
  MasterDetail masterdeta0_ 
left outer join
  Master master1_ 
   on masterdeta0_.MasterDetailId=master1_.MasterId 
where
  master1_.Name like (@p0+'%');
@p0 = 'A' [Type: String (4000:0:0)]

When a query involves an operation with a field of an entity connected one-to-one, NHibernate generates SQL with a left outer join.
Why is a left outer join used? I think an inner join would be better in this case.

And if I rewrite query in this way:

var query2 = _session.Query<MasterDetail>()
                      .Where(m => m.Master.Name != null)
                      .Where(m => m.Master.Name.StartsWith("A"))
                      .ToList();

The generated sql will be with inner join:

select
  masterdeta0_.MasterDetailId as masterdetailid1_1_,
  masterdeta0_.Type as type2_1_ 
from
  MasterDetail masterdeta0_ 
inner join
  Master master1_ 
    on masterdeta0_.MasterDetailId=master1_.MasterId 
where
  (
     master1_.Name is not null
  ) 
  and (
    master1_.Name like (@p0+'%')
  );
@p0 = 'A' [Type: String (4000:0:0)]

Here are my classes:

public class Master
  {
    public virtual int MasterId { get; set; }
    public virtual string Name { get; set; }
  }

  public class MasterDetail
  {
    public virtual int MasterDetailId { get; set; }
    public virtual int Type { get; set; }
    public virtual Master Master { get; set; }
  }

Here is the mapping:

<class name="Master">
    <id name="MasterId"></id>
    <property name="Name" not-null="true"/>
  </class>

  <class name="MasterDetail">
    <id name="MasterDetailId"></id>
    <property name="Type" not-null="true"/>
    <one-to-one name="Master"/>
  </class>