Question

我在我的一个项目中使用BLToolKit，我试图让它工作。我不喜欢的是我试图将一堆临时值平均分到一分钟，但正在生成的select语句按分钟分组然后选择原始时间。我认为我正在正确地做linq表达式（但是再次，我没有得到我期望的结果）。（这是C＃，如果你关心）任何人都知道出了什么问题？

                 var test = (from r in db.SensorReadingRaws
                        where r.TimeLogged < DateTime.Now.AddMinutes(-2)
                        group r by new
                        {
                            Sensor = r.SensorNumber,
                            //group time down to the minute
                            Time = r.TimeLogged.AddSeconds(-1 * r.TimeLogged.Second).AddMilliseconds(-1 * r.TimeLogged.Millisecond)
                        } into grouped
                        select new SensorReading
                        {
                            SensorNumber = grouped.Key.Sensor,
                            TimeLogged = grouped.Key.Time,
                            Reading = (int)grouped.Average(x => x.Reading)
                        }).ToList();

            textBox1.Text = db.LastQuery;

，结果查询是

SELECT
[r].[SensorNumber],
[r].[TimeLogged],
Avg([r].[Reading]) as [c1]
FROM
[SensorReadingRaw] [r]
WHERE
[r].[TimeLogged] < @p1
GROUP BY
[r].[SensorNumber],
DateAdd(Millisecond, Convert(Float, -DatePart(Millisecond, [r].[TimeLogged])), DateAdd(Second, Convert(Float, -DatePart(Second, [r].[TimeLogged])), [r].[TimeLogged])),
[r].[TimeLogged]

Answer 1

我发现了

BLToolkit.Data.Linq.Sql.AsSql<T>(T obj)

可用作此案例的解决方法。

将此功能应用于select语句中所需的分组键属性时，您将摆脱分组/选择原始字段。

它可能看起来像：

_queryStore.Leads().
    GroupBy(x => new {
        x.LeadDate.Hour,
        x.LeadDate.Minute
    }).
    Select(x => new {
        Hour = Sql.AsSql(x.Key.Hour),
        Minute = Sql.AsSql(x.Key.Minute),
        Count = x.Count()
    });

在您的特定情况下：

                 var test = (from r in db.SensorReadingRaws
                        where r.TimeLogged < DateTime.Now.AddMinutes(-2)
                        group r by new
                        {
                            Sensor = r.SensorNumber,
                            //group time down to the minute
                            Time = r.TimeLogged.AddSeconds(-1 * r.TimeLogged.Second).AddMilliseconds(-1 * r.TimeLogged.Millisecond)
                        } into grouped
                        select new SensorReading
                        {
                            SensorNumber = grouped.Key.Sensor,
                            TimeLogged = Sql.AsSql(grouped.Key.Time),
                            Reading = (int)grouped.Average(x => x.Reading)
                        }).ToList();

Answer 2

我昨天得到了同样的问题。今天我找到了解决方法。想法是编写2个 linq 查询。首先转换数据，然后对结果进行分组：

var bandAndDate =
    (from r in repo.Entities
    select new {Band = r.Score / 33, r.StartTime.Date});

var examsByBandAndDay =
    (from r in bandAndDate
    group r by new {r.Band, r.Date } into g
    select new { g.Key.Date, g.Key.Band, Count = g.Count() }).ToList();

这两个查询都运行一个执行该任务的SQL：

SELECT
    [t1].[c1] as [c11],
    [t1].[c2] as [c21],
    Count(*) as [c3]
FROM
(
    SELECT
        [r].[Score] / 33 as [c2],
        Cast(Floor(Cast([r].[StartTime] as Float)) as DateTime) as [c1]
    FROM
        [Results] [r]
) [t1]
GROUP BY
    [t1].[c2],
    [t1].[c1]

BLToolKit，Linq Query，SQL不是我的预期

2 个答案: