将此SQL查询转换为LINQ查询

Question

我想将这个 sql 查询转换为 linq 查询。

SELECT
  CreationUtcTime,
  Speed,
  convert((CreationUtcTime - LAG(CreationUtcTime) OVER (ORDER BY CreationUtcTime)), char) AS diff
FROM assetstatusrecords
WHERE
  Speed <> 0.00 and
  CreationUtcTime <= '2022-03-28' and
  CreationUtcTime >= '2022-02-21' and
  AssetId = '7556d50c-95e5-4cd5-a31d-b4d6c6ab1fb1'
ORDER BY CreationUtcTime

LINQ 的模型类

class AssetStatusRecord : Entity
    {
        protected AssetStatusRecord()
        {
        }

        public AssetStatusRecord(CoordinatesValue coordinates, double speed,
            LengthValue distanceTravelled, Guid sensorId, Guid? assetId,
            int? heading, Guid readingId, DateTime? sensorDateTime)
        {
            Coordinates = coordinates;
            Speed = speed;
            DistanceTravelled = distanceTravelled;
            SensorId = sensorId;
            AssetId = assetId;
            Heading = heading;
            ReadingId = readingId;
            SensorDateTime = sensorDateTime;
        }
        public CoordinatesValue Coordinates { get; private set; }
        public double Speed { get; private set; }
        public LengthValue DistanceTravelled { get; private set; }
        public Guid SensorId { get; private set; }
        public Guid? AssetId { get; private set; }
        public int? Heading { get; private set; }
        public Guid ReadingId { get; private set; }
        public DateTime? SensorDateTime { get; private set; }
    }

和实体类如下： -

public class Entity : IEntity
    {
        public Entity();

        public Guid Id { get; protected set; }
        public long SequentialId { get; protected set; }
        public DateTime CreationUtcTime { get; protected set; }
        public DateTime CreationLocalTime { get; protected set; }
    }

和接口 IEntity ：-

public interface IEntity
   {
       Guid Id { get; }
       long SequentialId { get; }
       DateTime CreationUtcTime { get; }
   }

该模型类可用于执行 linq 查询，我在下面的查询中使用它

Answer 1

如果您使用的是EF Core，则可以通过

使用此扩展程序，您可以在LINQ查询中使用lag：

var query = 
    from s in context.AssetStatusRecord.ToLinqToDB()  // switch LINQ Provider
    where s.Speed != 0 
        && s.CreationUtcTime <= endTime
        && s.CreationUtcTime >= startTime
        && s.AssetId == assetId
    orderby s.CreationUtcTime
    select new 
    {
        s.CreationUtcTime,  
        s.Speed,
        diff = s.CreationUtcTime - 
            Sql.Ext.Lag(s.CreationUtcTime)
                .Over()
                .OrderBy(s => s.CreationUtcTime)
                .ToValue()
    };

 var result = query.ToList();

Answer 2

如果对于任何两个记录a和b，则a.SequentionId＆lt; B. sequeTentialID条件a.creationutctime＆lt; = b.creationutctime被满足，然后没有lag lag函数您可以做类似的事情：

DateTime dateFrom = DateTime.Parse("2022-02-21");
DateTime dateTo = DateTime.Parse("2022-03-28");
string assetId = "7556d50c-95e5-4cd5-a31d-b4d6c6ab1fb1";

var records = 
    from rec in context.AssetStatusRecords
    where 
        rec.CreationUtcTime >= dateFrom && 
        rec.CreationUtcTime <= dateTo && 
        rec.Speed != 0 &&
        rec.AssetId == assetId
    select rec;

var query =
    from rec1 in records
    from rec2 in records.Where(r => rec1.SequentialId > r.SequentialId).DefaultIfEmpty()
    group new { rec1, rec2 } by new { rec1.SequentialId, rec1.CreationUtcTime, rec1.Speed } into g
    orderby g.Key.SequentialId
    select new
    {
        g.Key.CreationUtcTime,
        g.Key.Speed,
        Diff = EF.Functions.DateDiffDay(g.Max(p => p.rec2.CreationUtcTime), g.Key.CreationUtcTime)
    };

var results = query.ToList();

注意：上面的代码：与 pomelo.entityframeworkcore.mysqore.mysql 提供者。