NHibernate的QueryOver组由不选择按列分组 [英] NHibernate QueryOver group by without selecting the grouped by column

问题描述

有类似下面的查询：

var subquery = SessionFactory.GetCurrentSession()
    .QueryOver<SomeEntity>()
    .Where(_ => _.SomeOtherEntity.Id == someId)
    .SelectList(list => list
        .SelectGroup(x => x.SomeGroupByProperty)
        .SelectMax(x => x.MaxPerGroupProperty))
    .List<dynamic>();

生成的SQL是选择这两个 SomeGroupByProperty 和最大 MaxPerGroupProperty 的。是否有可能得到它的小组 SomeGroupByProperty ，但只能选择最高 MaxPerGroupProperty 的？这是使用子查询结果与父查询中包含

The generated sql is selecting both SomeGroupByProperty and maximum of MaxPerGroupProperty. Is it possible to get it to group on SomeGroupByProperty but only select maximum of MaxPerGroupProperty? This is for using the subquery result with a contains in parent query.

推荐答案

这是在NHibernate的JIRA一个开放的问题（标准查询）：的 https://nhibernate.jira.com/browse/NH-1426

It's an open issue in NHibernate jira (criteria query): https://nhibernate.jira.com/browse/NH-1426

您可以像下面这样做虽然

You can do it like this though

var subquery =
    QueryOver.Of<SomeEntity>()
        .Where(_ => _.SomeOtherEntity.Id == someId)
        .Select(
            Projections.ProjectionList()
                .Add(Projections.SqlGroupProjection("max(MaxPerGroupProperty) as maxAlias", "SomeGroupByProperty",
                    new string[] { "maxAlias" }, new IType[] { NHibernate.NHibernateUtil.Int32 })));

var parentQuery = session.QueryOver<SomeEntity2>()
    .WithSubquery.WhereProperty(x => x.MaxPerGroupPropertyReference).In(subquery).List();

不太为pretty与使用实体属性，但它确实工作。

Not quite as pretty as using the entity properties, but it does work.

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