NHibernate 中是否有算术运算预测? [英] Are there any arithmetic operation projections in NHibernate?

问题描述

我想从 NHibernate 获取这个 SQL:

I would like to get this SQL from NHibernate:

SELECT SUM(color_pages) * SUM(total_pages)
FROM connector_log_entry
GROUP BY department_name

但我在任何地方都找不到任何算术运算 (*) 投影.

But I can't find any arithmetic operation (*) projections anywhere.

这是我目前的代码:

Session.QueryOver<ConnectorLogEntry>()
       .SelectList(list => list
           .SelectGroup(m => m.DepartmentName)
           .WithAlias(() => dto.Department)
           .Select(Projections.Sum<ConnectorLogEntry>(m => m.TotalPages))
           //.Select(Projections.Sum<ConnectorLogEntry>(m => m.ColorPages))
           .WithAlias(() => dto.TotalColorPercentage))
       .TransformUsing(Transformers.AliasToBean<DepartmentConsumption>());

推荐答案

可以通过 VarArgsSQLFunction SQL 函数在条件查询中使用算术运算符.在您的特定情况下，这看起来像:

Arithmetic operators can be used in criteria queries via the VarArgsSQLFunction SQL function. In your particular case, this would look something like:

Session.QueryOver<ConnectorLogEntry>()
    .SelectList(list =>
        list.SelectGroup(m => m.DepartmentName)
            .WithAlias(() => dto.Department)
            .Select(Projections.SqlFunction(
                new VarArgsSQLFunction("(", "*", ")"),
                NHibernateUtil.Int32,
                Projections.Sum<ConnectorLogEntry>(m => m.TotalPages),
                Projections.Sum<ConnectorLogEntry>(m => m.ColorPages)))
            .WithAlias(() => dto.TotalColorPercentage))
    .TransformUsing(Transformers.AliasToBean<DepartmentConsumption>());

此技术将字符串直接注入生成的 SQL，因此您需要确保底层数据库支持您使用的运算符.

This technique injects strings directly into the generated SQL, so you'll need to make sure the underlying database supports the operators you use.

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