Fluent NHibernate QueryOver 在子查询上失败

Question

我有一个 table，它有 datetime 字段和 nvarchar 字段。我正在尝试执行一个查询，使用 Fluent Nhibernate QueryOver 仅获取每个 nvarchar 字段的最新行。

Table 在这里：

CREATE TABLE [dbo].[DataItem] (
    [Id]           INT           IDENTITY (1, 1) NOT NULL,
    [Source]       NVARCHAR (50) NULL,
    [Target]       NVARCHAR (50) NULL,
    [SendDateTime] DATETIME      NULL,
    [Version]      INT           NULL
);

QueryOver 代码在这里：

DataItem dataItemAlias = null;

        var c = QueryOver.Of<DataItem>(() => dataItemAlias);

        c.WhereRestrictionOn(x => x.Source).IsInsensitiveLike("A");

        DataItem maxSendDateTimeAlias = null;

        var subQuery = QueryOver.Of<DataItem>(() => maxSendDateTimeAlias)
            .Select(Projections.ProjectionList()
            .Add(Projections.Max(() => maxSendDateTimeAlias.SendDateTime))
            .Add(Projections.Group(() => maxSendDateTimeAlias.Target)))
            .Where(() => dataItemAlias.Source == maxSendDateTimeAlias.Source);

        c.WithSubquery.WhereProperty(p => p.SendDateTime).In(subQuery);
        var result = c.GetExecutableQueryOver(Session).List<DataItem>();

这是 SQL 查询：

SELECT this_.ID as ID0_0_, this_.Source as Source0_0_, this_.Target as Target0_0_, this_.SendDateTime as SendDate4_0_0_, this_.Version as Version0_0_ FROM [DataItem] this_ 
WHERE lower(this_.Source) like 'a' and this_.SendDateTime in (SELECT max(this_0_.SendDateTime) as y0_, this_0_.Target as y1_ 
    FROM [DataItem] this_0_ WHERE this_.Source = this_0_.Source GROUP BY this_0_.Target)

如果我删除

this_0_.Target as y1_

来自

SELECT max(this_0_.SendDateTime) as y0_, this_0_.Target as y1_ FROM [DataItem] this_0_...

这是正确的查询，我得到了正确的结果。

这是我得到的错误：

"Only one expression can be specified in the select list when the subquery is not introduced with EXISTS."

Here are the sources

Answer 1

是的，这个错误是真实存在的，这是一个解决方法

var subQuery =
QueryOver.Of<DataItem>()
    .Select(
        Projections.ProjectionList()
            .Add(Projections.SqlGroupProjection("max(SendDateTime) as maxSendDateTimeAlias", "Target",
                new string[] { "maxAlias" }, new IType[] { NHibernate.NHibernateUtil.Int32 })));

从

得到答案

Fluent NHibernate QueryOver 在子查询上失败

Fluent NHibernate QueryOver fails on subquery

sql

sql-server

fluent-nhibernate