Question

我有以下部分Linq查询：

var query = from ri in RouteInstance
        join rir in RouteInstanceRules on ri.RouteInstanceID equals rir.RouteInstanceID
        join rl in RoutingLocation on rir.RoutingLocationID equals rl.RoutingLocationID
        join rlh in RoutingLocationHistory on rl.RoutingLocationID equals rlh.RoutingLocationID
        where rlh.RouteTakenTime >= new System.DateTime(2011,2,4) && rlh.RouteTakenTime <= new System.DateTime(2011,2,5)

There is a 1:M relationship between RouteInstance and RouteInstanceRules
There is a 1:M relationship between RouteInstanceRules and RoutingLocation
There is a 1:M relationship between RoutingLocation and RoutingLocationHistory

由于这些关系是使用FK强制执行的，因此对于L2S是已知的，因此我应该能够在不使用'join'关键字的情况下构造此查询。但是，我很难过如何去做。

感谢。

Answer 1

你想要RouteInstances吗？如果是这样的话：

var query = DataContext.RoutingLocationHistory
           .Where(rlh => rlh.RouteTakenTime >= new System.DateTime(2011,2,4) 
                        && rlh.RouteTakenTime <= new System.DateTime(2011,2,5))
           .Select(rlh => rlh.RoutingLocation.RouteInstanceRule.RouteInstance)
           .Distinct();

Answer 2

我测试了像你这样的场景并获得了相同的结果你可以选择很多没有加入的东西，比如：

var query = from ri in RouteInstance
            from rir in RouteInstanceRules 
            from   rl in        RoutingLocation
            from    rlh in RoutingLocationHistory 
             where    ri.RouteInstanceID ==    rir.RouteInstanceID &&
             rir.RoutingLocationID == rl.RoutingLocationID &&
             rl.RoutingLocationID == rlh.RoutingLocationID &&
             rlh.RouteTakenTime >= new System.DateTime(2011,2,4) && rlh.RouteTakenTime <= new System.DateTime(2011,2,5)

Answer 3

检查dbml设计器中的关联。如果它注意到您的外键，它将自动创建关联。如果不是 - 您可以自己添加它们（即使外键不存在或未强制执行）。

通过查询关联属性，您可以隐藏关系详细信息。

query =
  from ri in dataContext.RouteInstances
  from rir in ri.RouteInstanceRules
  from rl in rir.RoutingLocations
  from rlh in rl.RoutingLocationHistories
  where rlh.RouteTakenTime >= new System.DateTime(2011,2,4)
    && rlh.RouteTakenTime <= new System.DateTime(2011,2,5)

如果你想要与Guillaume86的答案类似的结果，但没有明显的...那么这个子查询过滤器。

IQueryable<RouteInstance> query =
   from ri in dataContext.RouteInstances
   where ri.RouteInstanceRules
     .Any(rir => rir.RoutingLocations
       .Any(rl => rl.RoutingLocationHistories
         .Any(rlh => rlh.RouteTakenTime >= new System.DateTime(2011,2,4)
           && rlh.RouteTakenTime <= new System.DateTime(2011,2,5)
         )
       )
     )
   select ri;

Linq - 如何在没有'join'关键字的情况下构建此查询？

3 个答案: