BLToolKit，LinqQuery，SQL不是我所期望的

Question

我正在我的一个项目中使用BLToolKit，我正试图让它发挥作用。我不喜欢的是，我试图将一堆temp平均到一分钟，但生成的select语句按分钟分组，然后选择原始时间。我认为我做linq表达式是正确的（但话说回来，我没有得到我期望的结果）。（如果你在乎的话，这是C#）有人知道出了什么问题吗？

                 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;

得到的查询就是这个

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

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

可以用作这种情况的变通方法。

当将此函数应用于select语句中所需的分组键属性时，您可以摆脱对原始字段的分组/选择。

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()
    });

在您的特殊情况下：

                 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

我昨天也遇到了同样的问题。今天我找到了一个变通办法。这个想法是编写2linq查询。首先对数据进行转换，第二次对结果进行分组：

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SQL来完成这项工作：

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]