NHibernate QueryOver join syntax for multiple tables

Question

How would I rewrite this SQL using QueryOver? I'm not sure how QueryOver's join precedence and resolution works.

SELECT DISTINCT T1.*
FROM T1
LEFT JOIN T2
   JOIN T3
   ON T2.T3Key = T3.PrimaryKey
ON T1.PrimaryKey = T2.T1Key
LEFT JOIN T4
   JOIN T5
   ON T4.T5Key = T5.PrimaryKey
ON T1.PrimaryKey = T4.T1Key
WHERE T3.Criteria = @Criteria
OR T5.Criteria = @Criteria

http://www.sqlfiddle.com/#!3/affd13/5

Answer 1

Assuming you have all the relationships setup, it's a matter of setting up alias variable to use in the QueryOver...

T2 t2Alias = null;
T3 t3Alias = null;
T4 t4Alias = null;
T5 t5Alias = null;

int criteria = 1;

var results = Session.QueryOver<T1>()
    .Left.JoinAlias(x => x.T2, () => t2Alias)
    .Left.JoinAlias(() => t2Alias.T3, () => t3Alias)
    .Left.JoinAlias(x => x.T4, () => t4Alias)
    .Left.JoinAlias(() => t4Alias.T5, () => t5Alias)
    .Where(Restrictions.Disjunction()
        .Add(Restrictions.Where(() => t3Alias.Criteria == criteria))
        .Add(Restrictions.Where(() => t5Alias.Criteria == criteria)))
    .TransformUsing(Transformers.DistinctRootEntity)
    .List();

I don't think you'll be able to nest those inner joins...but it looks like you'd get the same results with all left joins.