实体框架4没有映射属性的困难查询

本文关键字：查询 属性 映射 框架 实体 | 更新日期: 2023-09-27 18:08:45

我是EF的新手，我认为有时牺牲ORM的优势更容易。但是我想知道是否有一种方法可以使用EF4来执行这个查询。

我有数据仓库与事实表。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; } 
    }

和查询sql 

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查询意味着(我想获得特定球队与其他球队的比赛结果(特定球队获胜的比赛次数，以及特定球队较弱的比赛次数))

实体框架4没有映射属性的困难查询

_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、输的总和。

对于第二个查询，您可以直接连接与第一个查询类似的查询:

_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()
       })
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