具有未映射属性的实体框架 4 困难查询答案

【问题标题】：Entity Framework 4 difficult query with not mapped property具有未映射属性的实体框架 4 困难查询
【发布时间】：2013-04-12 12:22:35
【问题描述】：

我是EF 的新手，我认为有时候牺牲ORM 的优势更容易。但我想知道是否有办法使用EF4 执行此查询。

我有带有事实表的数据仓库。映射看起来像

    public class GameResult
    {
        [Key]
        public int GameResultId { get; set; } 

        public virtual Competition Competition { get; set; }    

        public virtual CustomDate DateGame { get; set; }     

        public virtual Contender ContenderFirst { get; set; }  

        public virtual Contender ContenderSecond { get; set; } 

        public virtual Location Location { get; set; }

        public int ScoreContenderFirst { get; set; }

        public int ScoreContenderSecond { get; set; }

        public int PrizeStock { get; set; }

        public int Budget { get; set; }

        [NotMapped]
        public int WinCount { get; set; }

        [NotMapped]
        public int FailCount { get; set; }

        [NotMapped]
        public int DeadHeatCount { get; set; }

        [NotMapped]
        public int CountGames { get; set; } 
    }

并在sql查询

select 
    Contenders.Name,
    sum((Case 
        when (ScoreContenderFirst > ScoreContenderSecond) then 1
        else 0
    end)) as wins,
    sum ((Case 
        when (ScoreContenderFirst = ScoreContenderSecond) then 1
        else 0
    end)) as equals,
    sum((Case 
        when (ScoreContenderFirst < ScoreContenderSecond) then 1
        else 0
    end)) as fail,
    COUNT(GameResults.GameResultId)as countGames
from GameResults 
inner join Contenders
on GameResults.ContenderSecond_ContenderId = Contenders.ContenderId
where GameResults.ContenderFirst_ContenderId = 42 
group by Contenders.Name 
UNION 
select 
    Contenders.Name,
    sum((Case 
        when (ScoreContenderFirst < ScoreContenderSecond) then 1
        else 0
    end)) as wins,
    sum ((Case 
        when (ScoreContenderFirst = ScoreContenderSecond) then 1
        else 0
    end)) as equals,
    sum((Case 
        when (ScoreContenderFirst > ScoreContenderSecond) then 1
        else 0
    end)) as fail,
    COUNT(GameResults.GameResultId)as countGames
from GameResults 
inner join Contenders
on GameResults.ContenderFirst_ContenderId = Contenders.ContenderId
where GameResults.ContenderSecond_ContenderId = 42 
group by Contenders.Name

这个sql 查询的意思是（我想获取特定球队与其他球队的比赛结果（特定球队获胜的比赛数量，以及特定球队较松的比赛数量））

【问题讨论】：

也许您可以解释一下您的 SQL 请求返回什么，即它的目标是什么。
为什么将聚合结果存储在每个单独的对象中，而不是存储在不属于 EF 模型的另一个特定结果类中？
@GertArnold 我找到了两种方法stackoverflow.com/questions/1987836/… 和stackoverflow.com/questions/5155853/…。并决定为什么不将聚合结果保存为 [Not Mapped] 对象。请提供您的解决方案
我想说的是，将聚合结果存储在构成聚合的对象中是没有意义的。你最终会得到例如GameResult.WinCount。 GameResult 有两个竞争者，那么是谁呢？而GameResult大约是1场比赛，算一场比赛是什么意思？所以我的意思是：属性不应该放在首位，你需要一个聚合的结果类。这不是如何处理未映射的属性的问题。

标签： c# entity-framework-4 union data-warehouse

【解决方案1】：

_efContext.GameResult
          .Where(game => game.ContenderFirst_ContenderId  == 42)
          .Select(game => new { 
                    ContendersName = game.ContenderFirst.Name
                  , Win = game.ScoreContenderFirst > game.ScoreContenderSecond
                  , Draw = game.ScoreContenderFirst == game.ScoreContenderSecond
                  , Lose = game.ScoreContenderFirst < game.ScoreContenderSecond
                  })
          .GroupBy(game => game.ContendersName)
          .Select(grp => new {
                  ContendersName= grp.Key
                , Wins = grp.Where(game => game.Win).Count()
                , Draws = grp.Where(game => game.Draw).Count()
                , Loses = grp.Where(game => game.Lose).Count()
           })

不包括 countGames，因为它只是赢、平和输的总和。

对于第二个，你可以加入这个看起来像第一个的查询：

_efContext.GameResult
          .Where(game => game.ContenderSecond_ContenderId  == 42)
          .Select(game => new { 
                ContendersName = game.ContenderSecond.Name
              , Win = game.ScoreContenderFirst < game.ScoreContenderSecond
              , Draw = game.ScoreContenderFirst == game.ScoreContenderSecond
              , Lose = game.ScoreContenderFirst > game.ScoreContenderSecond
              })
          .GroupBy(game => game.ContendersName)
          .Select(grp => new {
              ContendersName= grp.Key
            , Wins = grp.Where(game => game.Win).Count()
            , Draws = grp.Where(game => game.Draw).Count()
            , Loses = grp.Where(game => game.Lose).Count()
       })

【讨论】：

我不明白你要我做什么？
我不理解您查询的结果类型