以下 SQL 查询的 LINQ 等效项是什么？

问题描述

T-sql 查询：

 SELECT  T1.ID,T1.UserId,T1.ServerId,T1.diskId,T1.Date_ PrevIoUsDate_,T1.Row,MIN(T2.Date_) AS Date_,DATEDIFF(MINUTE,T1.Date_,MIN(T2.Date_)) AS MinutesDiff
FROM    IesLogs T1
        LEFT JOIN IesLogs T2
            ON T1.diskId = T2.diskId
            where T1.diskId = 2 AND T2.Date_ > T1.Date_ AND T1.Row = T2.Row
GROUP BY T1.ID,T1.[Row]
ORDER BY T1.diskId,T1.[Row],T1.Id

我获得的数据比我预期的要多。

  var result = (
                    from i in context.IesLogs
                    join i2 in context.IesLogs 
                        on i.diskId equals diskId into i2left
                    from i3 in i2left.DefaultIfEmpty()
                    where 
                        i.UserId == userId
                        && i3.Date > i.Date
                        && i.Row == i3.Row
                    group i3 by new {i.Id,i.ServerId,i.diskId,i.Row,PrevIoUsDate = i.Date,i3.Date} into logs
                    orderby logs.Key.diskId,logs.Key.Row,logs.Key.Id  ascending
                    select new IesLogStatisticsDto
                    {
                        Id = logs.Key.Id,ServerId = logs.Key.ServerId,diskId = logs.Key.diskId,PrevIoUsDate = logs.Key.PrevIoUsDate,Date = logs.Min(x => x.Date),Row = logs.Key.Row,DateDiff = Convert.ToInt32((logs.Min(x => x.Date) - logs.Key.PrevIoUsDate).TotalMinutes)
                    }).ToList();

我应该得到 6 个数据时却得到了 12 个。我该如何解决？

我认为我获得大量数据的原因是上面代码博客中的(i3.Date > i.Date) 但我必须实现这一行。

解决方法

您的 LINQ 查询分组错误。您必须从分组键中删除 i3.Date。

稍微重构：

var query =
    from i in context.IesLogs
    join i2 in context.IesLogs 
        on i.DiskId equals diskId into i2left
    from i2 in i2left.DefaultIfEmpty()
    where 
        i.UserId == userId
        && i2.Date > i.Date
        && i.Row == i2.Row
    group i2 by new {i.Id,i.ServerId,i.DiskId,i.Row,PreviousDate = i.Date} into logs
    orderby logs.Key.DiskId,logs.Key.Row,logs.Key.Id  ascending
    select new IesLogStatisticsDto
    {
        Id = logs.Key.Id,ServerId = logs.Key.ServerId,DiskId = logs.Key.DiskId,PreviousDate = logs.Key.PreviousDate,Date = logs.Min(x => x.Date),Row = logs.Key.Row,DateDiff = Convert.ToInt32((logs.Min(x => x.Date) - logs.Key.PreviousDate).TotalMinutes)
    };