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    <p>I've managed to resolve a similar problem by slightly adapting the original sql query. I've ended up with something like this (pseudo sql code):</p> <pre><code>SELECT p.* FROM [Items] as p WHERE EXISTS ( SELECT [childId] as childNodeId FROM [Items] as q WHERE p.[childId] = q.[childNodeId] GROUP BY q.[childId] HAVING p.[price] = MAX(q.[price]) ) </code></pre> <p>And this is the QueryOver implementation:</p> <pre><code>var subquery = QueryOver.Of(() =&gt; q) .SelectList(list =&gt; list.SelectGroup(() =&gt; q.ChildId)) .Where(Restrictions.EqProperty( Projections.Property(() =&gt; p.Price), Projections.Max(() =&gt; q.Price))) .And(Restrictions.EqProperty( Projections.Property(() =&gt; p.ChildId), Projections.Property(() =&gt; q.ChildId))); </code></pre> <p>From here you only need to pass the aliases so that NHibernate can resolve entities correctly (pseudo code):</p> <pre><code>var filter = QueryOver.Of(() =&gt; p) .WithSubquery.WhereExists(GetSubQuery(p, criteria...)); </code></pre> <p>I hope this helps in your particular case.</p> <p><strong>UPDATE:</strong> Criteria API</p> <pre><code>var subquery = DetachedCriteria.For&lt;Items&gt;("q") .SetProjection(Projections.ProjectionList() .Add(Projections.GroupProperty("q.ChildId"))) .Add(Restrictions.EqProperty("p.Price", Projections.Max("q.Price"))) .Add(Restrictions.EqProperty("p.ChildId", "q.ChildId")); var query = DetachedCriteria.For&lt;Items&gt;("p") .Add(Subqueries.Exists(subquery)); </code></pre> <p>Nevertheless I would recommend sticking to the <code>QueryOver</code> version, it's much more intuitive and you avoid magic strings (especially that you don't have to upgrade the NH version).</p> <p>Please let me know if this is working for you.</p>
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    1. COI'm a little confused. Is there a way to do this with the ICriteria API instead of QueryOver? I've not used QueryOver before, and this may be a complicated 'first example' :\
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    2. CO@GWLlosa: Can you confirm that the sql that I've posted in my answer works for you and that you get exactly the same results? I can than try to re-write the query with the Criteria API, btw which version of NHibernate are you using?
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    3. COThe SQL you have and the SQL I have do in fact produce the same rows. I'm using NHibernate 3.1.0.4000, according to the DLL details.
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