group by month and year parts using queryover

问题

I have a model, that contains a DateTime field and a Price field. I want to get a list that gives me an aggregation of month/year - price so for the data:

1. 15/01/2012 200
2. 16/01/2012 200
3. 15/02/2012 300
4. 16/02/2012 300
5. 15/03/2012 400
6. 16/03/2012 400

I will get:

1. 01/2012 400
2. 02/2012 600
3. 03/2012 800

So far I didn't find a way to achive this using QueryOver. I keep getting "could not resolve property" when i try to look at the Month/Year parts of the date.

Those questions:

Group posts by year, then by month

Group/Sort by Date Year/Month, Partial Select with NHibernate (Projection? Transformation?)

got answered using LINQ - not what I'm looking for.

Any ideas? Thanks

(using NHibernate 3.2)

回答1:

QueryOver is not a good choice because grouping will need to be done using a SQL expression. For this type of query, QueryOver is simply a pointless abstraction that adds no value.

If you must do it using QueryOver you could do something like:

session.QueryOver<...>()
   .SelectList(list => list
      .Select(GroupProperty(Projections.SqlProjection(...)))
      .SelectSum(x => x.Price)
   );

来源：https://stackoverflow.com/questions/10015732/group-by-month-and-year-parts-using-queryover