创建NHibernate Queryover以获得两个字段产品的总和

Question

我有两个表Invoice和InvoiceLineItem.该InvoiceLineItem表包含:

Id
InvoiceId
Quantity
UnitPrice 

列.我想创建NHibernate QueryOver语句来对发票行项目进行分组,InvoiceId并得到和的乘积之UnitPrice和Quantity

SQL就是这样.

SELECT InvoiceId, SUM(Quantity*UnitPrice) AS Total
  FROM InvoiceLineItem
GROUP BY InvoiceId

我用过,Projections.Sum但我不确定我们如何在其中增加两列(如果这是正确的方法).

Answer 1

它看起来并不是一个很好的方法.建立这个答案,你可以使用VarArgsSQLFunction:

InvoiceLineItem lineItemAlias = null;

session.QueryOver<InvoiceLineItem>(() => lineItemAlias)
    .SelectList(list => list
        .Select(Projections.Sum(
            Projections.SqlFunction(new VarArgsSQLFunction("(", "*", ")"),
            NHibernateUtil.Double,
            Projections.Property(() => lineItemAlias.Quantity),
            Projections.Property(() => lineItemAlias.UnitPrice))))
        .SelectGroup(() => lineItemAlias.Invoice.Id)
   // TransformUsing, List<>, etc.

这将生成如下所示的SQL:

SELECT
    sum((this_.Quantity*this_.UnitPrice)) as y0_,
    this_.InvoiceId as y1_
FROM
    InvoiceLineItem this_
GROUP BY
    this_.InvoiceId