8

我有下表

CREATE TABLE [dbo].[DeviceLogs](
    [DeviceLogId] [int] IDENTITY(1,1) NOT NULL,

    [UserId] [nvarchar](50) NULL,
    [LogDate] [datetime2](0) NULL,
)
GO

数据样本

   1     1    2013-05-29 11:05:15   //accepted (its the first occurance for userid 1)
   2     1    2013-05-29 11:05:20   //discarded (within 5 mins from 1st record)
   3     1    2013-05-29 11:07:56   //discarded (within 5 mins from 1st record)
   4     1    2013-05-29 11:11:15   //accepted (after 5 mins from 1st occurance)
   5     2    2013-05-29 11:06:05   //accepted (its the first occurance for userid 2)
   6     2    2013-05-29 11:07:18   //discarded (within 5 mins from 1st record)
   7     2    2013-05-29 11:09:38   //discarded (within 5 mins from 1st record)
   8     2    2013-05-29 11:12:15   //accepted (after 5 mins from 1st occurance)

我只想选择从先前选择的记录开始 5 分钟后发生的记录，包括数据集中的第一条记录

所需的输出是

 1     1     2013-05-29 11:05:15   
 4     1     2013-05-29 11:11:15
 5     2     2013-05-29 11:06:05 
 8     2     2013-05-29 11:12:15

我正在尝试 GroupBy 但没有给出日期

db.DeviceLogs.GroupBy(g=>new {g.LogDate.Year, 
                              g.LogDate.Month, 
                              g.LogDate.Day, 
                              g.LogDate.Hour, 
                              g.LogDate.Minutes, 
                              g.UserID})
             .Select(s=>new {UserID=s.Key.UserID, s.???});

先感谢您。

4

5 回答 5

5 
var result =
    from log in db.DeviceLogs
    let byId = 
        db.DeviceLogs.Where(item => item.UserId == log.UserId)
    let first =
        byId.First(item => item.LogDate == byId.Min(min => min.LogDate))
    where 
        log.Equals(first) || (log.LogDate - first.LogDate).Minutes > 5
    select log;
于 2013-05-29T08:20:44.150 回答
2

好的，怎么样。

var firstDates = db.DeviceLogs.GroupBy(d => d.UserId).ToDictionary(
    g => g.Key,
    g => g.OrderBy(d => d.LogDate).First().LogDate);

db.DeviceLogs.GroupBy(g => new
  {
    v = Math.Floor(SqlMethods.DateDiffMinute(firstDates[d.UserId], g.LogDate) / 5),
    u = g.UserID
  }).Select(s => s.OrderBy(s => s.LogDate).First());

我不确定您是否可以使用 linq to SQL 在一个查询中执行此操作。如果分钟数超过 32 位整数的最大值，则会出现潜在问题。

于 2013-05-29T08:21:48.530 回答
1

我可以建议你一个 SQL 解决方案：

SELECT  [DeviceLogId],[UserId],[LogDate] FROM (
    SELECT *,
          (SELECT top 1 [LogDate] FROM DeviceLogs t2
                      WHERE datediff(minute,t2.logDate,t1.logDate)>5
                      ORDER BY [LogDate] DESC) prev,
          (SELECT TOP 1 [Logdate] FROM DeviceLogs t3 
              WHERE t3.[LogDate]=
                    (SELECT MIN([LogDate])
                     FROM DeviceLogs t4 
                     WHERE t4.[UserId]=t1.[UserId])) first
    FROM DeviceLogs t1 ) tres
WHERE prev IS NOT NULL OR first=logdate

见提琴手http://sqlfiddle.com/#!6/fa74e/50

于 2013-05-29T08:35:39.963 回答
1

我不确定您是否可以使用单个 LINQ 语句来执行此操作，因为您需要记住最后产生的记录的 DateTime。您可以像这样使用迭代器块：

private static readonly TimeSpan MinimumTimeSpan = new TimeSpan(0,5,0);

IEnumerable<Record> getSparseRecords(IEnumerable<Record> allRecords)
{
    DateTime previous = DateTime.MinValue;
    foreach(var record in allRecords)
    {
        TimeSpan dif = record.DateTime - previous;
        if (dif >= MinimumTimeSpan)
        {
            previous = record.DateTime;
            yield return record;
        }
    }
}

其中 Record 将是一个表示单个记录的类，其中包括类型的 DateTime 属性DateTime（请参见此处）。如果您的LogDate属性是不同的类型，您可能需要稍微更改代码。

于 2013-05-29T08:36:25.237 回答
1

这是我的解决方案

class Program
{
    static void Main(string[] args)
    {
        List<DeviceLog> list = new List<DeviceLog>
            {
                new DeviceLog() { Id = 1, UserId = 1, LogDate = DateTime.Parse("2013-05-29 11:05:15") },
                new DeviceLog() { Id = 2, UserId = 1, LogDate = DateTime.Parse("2013-05-29 11:05:20") },
                new DeviceLog() { Id = 3, UserId = 1, LogDate = DateTime.Parse("2013-05-29 11:07:56") },
                new DeviceLog() { Id = 4, UserId = 1, LogDate = DateTime.Parse("2013-05-29 11:11:15") },

                new DeviceLog() { Id = 5, UserId = 2, LogDate = DateTime.Parse("2013-05-29 11:06:05") },
                new DeviceLog() { Id = 6, UserId = 2, LogDate = DateTime.Parse("2013-05-29 11:07:18") },
                new DeviceLog() { Id = 7, UserId = 2, LogDate = DateTime.Parse("2013-05-29 11:09:38") },
                new DeviceLog() { Id = 8, UserId = 2, LogDate = DateTime.Parse("2013-05-29 11:12:15") },
            };

        list = list.Where(l => (l.Id == list.Where(g => g.UserId == l.UserId).Min(h => h.Id))
            || (l.LogDate - list.Where(g => g.UserId == l.UserId).OrderBy(m => m.Id).First().LogDate).Minutes > 5 ).ToList();


    }


}

class DeviceLog
{
    public int Id { get; set; }

    public int UserId { get; set; }

    public DateTime LogDate { get; set; }

}
于 2013-05-29T08:47:51.760 回答