Question

我有以下SQL查询：

goto

我发现了两个LINQ查询。

select 
    [Event2].EventType AS 'Event type', 
    SUM (1)            AS 'Number of events', 
    AVG(DATEDIFF(Second, [Event1].CreationDate, [Event2].CreationDate)) AS 'Time'
from [Event] as [Event1]
join [Event] as [Event2] on [Event1].Id = [Event2].ParentId
group by [Event2].EventTypeId;

我必须将这些查询合并为一个。结果必须包含三个元素：第一个事件的创建日期和第二个事件的创建日期之间经过的时间// This query brings the event types and the differences between the events. var rows = from event1 in _eventRepository.AsQueryable() join event2 in _eventRepository.AsQueryable() on event1.Id equals event2.ParentId select new { EventId = event2.EventId, TimeInSeconds = DbFunctions.DiffSeconds(event1.CreationDate, event2.CreationDate) }; // This query groups the rows before by Event type. var groups = (from item in rows group item by item.EventTypeId into g select new EventModel { EventTypeId = g.Key, NumberOfEvents = g.Sum(x => 1), Time = (int) g.Average(x => x.TimeInSeconds) }).ToList();，Event Type，The number of events。

Answer 1

您应该只将分组语句添加到第一个查询（而不是选择）：

var result = (from event1 in _eventRepository
              join event2 in _eventRepository on event1.Id equals event2.ParentId

              group new {
                EventId =  event2.EventId,
                TimeInSeconds = DbFunctions.DiffSeconds(event1.CreationDate, event2.CreationDate)
              }
              by event2.EventTypeId into g

              select new EventModel {
                EventTypeId = g.Key,
                NumberOfEvents = g.Count(),
                Time = (int) g.Average(x => x.TimeInSeconds)
              }).ToList();

您也不能在分组中指定字段，但只能在select语句中指定，但将其保留为原始

如何将两个LINQ查询合并到一个查询中？

1 个答案: