c# – SQL> Linq to Sql,SQL Query工作,Linq to SQL返回空数据集

2023年6月10日 195次阅读

我有这个SQL查询工作：

select sum(dbos.Points) as Points, dboseasons.Year 
    from dbo.StatLines dbos
    inner join dbo.Games dbog on dbog.GameId = dbos.GameId
    inner join dbo.Seasons dboseasons on dbog.Season_SeasonId = dboseasons.SeasonId
    where dbos.PlayerId = 3
    group by dboseasons.Year

它返回积分,年份(56,2016)

我正在尝试将此转换为Linq查询以与EF一起使用.

我有

var query =
            from dbostats in _db.StatLines
            join dbogames in _db.Games on dbostats.GameId equals dbogames.GameId
            join dboseasons in _db.Seasons on dbogames.Season.SeasonId equals dboseasons.SeasonId
            where dbostats.PlayerId == player.PlayerId
            group dbostats.Points by dboseasons.Year into g
            select new
            {
                Year = g.Key,
                Points = g.Sum()
            };

        playerAndStatLines.StatLinesBySeason =
            query
            .ToList()
            .Select( r => new StatsBySeason
                {
                    Season = r.Year,
                    Points = r.Points
                });

WHich返回空结果集.

当我查看它生成的SQL时,就是这样

SELECT 
[GroupBy1].[K1] AS [Year], 
[GroupBy1].[A1] AS [C1]
FROM ( SELECT 
    [Extent3].[Year] AS [K1], 
    SUM([Extent1].[Points]) AS [A1]
    FROM   [dbo].[StatLines] AS [Extent1]
    INNER JOIN [dbo].[Games] AS [Extent2] ON [Extent1].[GameId] = [Extent2].[GameId]
    INNER JOIN [dbo].[Seasons] AS [Extent3] ON [Extent2].[Season_SeasonId] = [Extent3].[SeasonId]
    WHERE ([Extent1].[Discriminator] IN (N'StatsBySeason',N'StatLines')) AND ([Extent1].[PlayerId] = 3)
    GROUP BY [Extent3].[Year]
)  AS [GroupBy1]

正如预期的那样,对我的数据库执行时返回一个空结果集.

这个问题似乎是这样的：

([Extent1].[Discriminator] IN (N'StatsBySeason',N'StatLines')) AND

如果我把它拿出并运行生成的查询,那么我会回到2016年,56结果.

什么是这个Extent1.Discriminator,为什么它从我的linq查询生成它？

我的MOdel课程：

public class PlayerAndStatLines
    {
        public PlayerWithTeam PlayerWithTeam { get; set; }
        public IEnumerable<StatsBySeason> StatLinesBySeason { get; set; }
    }


public class Season
    {
        public int SeasonId { get; set; }
        public int Year { get; set; }
    }


public class Game
    {
        public int GameId { get; set; }
        public int HomeTeamId { get; set; }
        public int AwayTeamId { get; set; }
        public int HomeScore { get; set; }
        public int AwayScore { get; set; }
        public DateTime DatePlayed { get; set; }
        public GameType GameType { get; set; }
        public int? PlayoffGameNumber { get; set; }
        public Season Season { get; set; }
    }

public class StatLines
    {
        public int StatLinesId { get; set; }
        public int GameId { get; set; }
        public int PlayerId { get; set; }
        public int TeamId { get; set; }
        public int Points { get; set; }
        public int DefensiveRebounds { get; set; }
        public int OffensiveRebounds { get; set; }
        public int Assists { get; set; }
        public int Turnovers { get; set; }
        public int Minutes { get; set; }
        public int Steals { get; set; }
        public int Blocks { get; set; }
        public int Fouls { get; set; }
        public int ThreePointFieldGoalsAttempted { get; set; }
        public int ThreePointFieldGoalsMade { get; set; }
        public int TwoPointFieldGoalsAttempted { get; set; }
        public int TwoPointFieldGoalsMade { get; set; }
        public int FreeThrowsMade { get; set; }
        public int FreeThrowsAttempted { get; set; }
        public bool Started { get; set; }
    }


public class StatsBySeason : StatLines
    {
        public int Season { get; set; }

        public string SeasonYears => Season + " / " + (Season + 1);
    }

如果我运行以下SQL：

select Discriminator from dbo.StatLines

我得到两排,都是空的.

谢谢.

最佳答案 在同一个程序集中继承实体类时要非常小心(尽可能避免). EF发现派生类并决定您要使用
TPH inheritance strategy并静默(如果您使用自动迁移)创建并使用Discriminator列,当然对于现有数据是空的并且会破坏您的查询.

我看到两个选择：

>用继承替换继承：

public class StatsBySeason
{
    public int Season { get; set; }
    public StatLines StatLines { get; set; }

    public string SeasonYears => Season + " / " + (Season + 1);
}

>让EF使用Fluent配置忽略StatsBySeason类：

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Ignore<StatsBySeason>();
    // ...
}

或数据注释：

[NotMapped]
public class StatsBySeason : StatLines
{
    // ...
}
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