左外连接 Lambda答案

【问题标题】：left outer join Lambda左外连接 Lambda
【发布时间】：2019-01-22 15:19:50
【问题描述】：

全部，

我有来自多个表的多个左外连接。我的 SQL 查询工作正常，如下所示：

    select distinct
    C.CUST_CD, C.DSC, C.BH_PHONE, A.ADDRESS, CITY.DESCR CITY, ZIP.DESCR ZIP, 
    CSH.UDT_DT , CSR.DSC 
    from 
    dbo.CUST C
    inner join dbo.CUST_ADDR A on C.CUST_CD = A.CUST_CD and A.ADDR_CD = 5   
    left outer join dbo.LOCATION CITY on A.CITY_CD = CITY.LOCATION_CD
    left outer join dbo.LOCATION ZIP on A.ZIP_CD = ZIP.LOCATION_CD
    left outer join dbo.CUST_STS S on C.CUST_STS_CD = S.CUST_STS_CD
    left outer join dbo.CUST_STS_HIS CSH on C.CUST_CD = CSH.CUST_CD
    left outer join dbo.CUST_STS_REASON CSR on CSH.REASON_CD = CSR.REASON_CD
    where 
      C.CUST_STS_CD in (5)
      and CSH.CUST_STS_CD in (5)
      and CSR.STS_CD in (5)  
      order by C.CUST_CD

我的 Lambda 表达式如下所示：

    var items =    (
                    from a in db.CUSTs

                    from b in db.CUST_ADDR
                         .Where(bb => bb.CUST_CD == a.CUST_CD && bb.ADDR_CD ==5)                           

                    from c in db.LOCATION
                         .Where(cc => cc.LOCATION_CD == b.CITY_CD)
                         .DefaultIfEmpty() // <== makes outer left join         

                    from d in db.LOCATION
                         .Where(dd => dd.LOCATION_CD == c.LOCATION_CD)
                         .DefaultIfEmpty()

                    from e in db.LOCATION
                        .Where(ee => ee.LOCATION_CD == b.ZIP_CD)
                        .DefaultIfEmpty() 

                    from f in db.CUST_STS_HIS
                       .Where(ff => ff.CUST_STS_CD == a.CUST_STS_CD)
                       .DefaultIfEmpty() 

                    from g in db.CUST_STS_REASON
                       .Where(gg => gg.STS_CD == f.CUST_STS_CD)
                       .DefaultIfEmpty() 

                    where (a.CUST_STS_CD == 5 && f.CUST_STS_CD == 5 && g.STS_CD == 5)

                    select new
                    {                           
                        CUSTCode = a.CUST_CD,
                        CUSTDesc = a.DSC,
                        CUSTPhone = a.BH_PHONE,
                        CUSTAddr = a.ADDRESS,
                        CUSTCity = c.DESCR,
                        CUSTZip = d.DESCR,
                        CUSTCounty = e.DESCR,
                        Date = f.UDT_DT,
                        reason = g.DSC

                    })
                    .ToList();

这是来自于 Lamda 表达式的 SQL：

    SELECT 
1 AS [C1], 
[Filter1].[CUST_CD1] AS [CUST_CD], 
[Filter1].[DSC] AS [DSC], 
[Filter1].[BH_PHONE] AS [BH_PHONE], 
[Filter1].[ADDRESS] AS [ADDRESS], 
[Filter1].[DESCR1] AS [DESCR], 
[Filter1].[DESCR2] AS [DESCR1], 
[Filter1].[DESCR3] AS [DESCR2], 
[Filter1].[UDT_DT] AS [UDT_DT], 
[Extent7].[DSC] AS [DSC1]
FROM   (SELECT [Extent1].[CUST_CD] AS [CUST_CD1], [Extent1].[DSC] AS [DSC], [Extent1].[BH_PHONE] AS [BH_PHONE], [Extent1].[ADDRESS] AS [ADDRESS], [Extent3].[DESCR] AS [DESCR1], [Extent4].[DESCR] AS [DESCR2], [Extent5].[DESCR] AS [DESCR3], [Extent6].[UDT_DT] AS [UDT_DT], [Extent6].[CUST_STS_CD] AS [CUST_STS_CD1]
    FROM      [DBO].[CUST] AS [Extent1]
    INNER JOIN (SELECT 
[CUST_ADDR].[CUST_CD] AS [CUST_CD], 
[CUST_ADDR].[ADDR_CD] AS [ADDR_CD], 
[CUST_ADDR].[ADDRESS] AS [ADDRESS], 
[CUST_ADDR].[CITY_CD] AS [CITY_CD], 
[CUST_ADDR].[ZIP_CD] AS [ZIP_CD], 
[CUST_ADDR].[STATE_CD] AS [STATE_CD], 
[CUST_ADDR].[ADDRESS2] AS [ADDRESS2]
FROM [DBO].[CUST_ADDR] AS [CUST_ADDR]) AS [Extent2] ON ([Extent2].[CUST_CD] = [Extent1].[CUST_CD]) AND (cast(5 as decimal(18)) = [Extent2].[ADDR_CD])
    LEFT OUTER JOIN [DBO].[LOCATION] AS [Extent3] ON [Extent3].[LOCATION_CD] = [Extent2].[CITY_CD]
    LEFT OUTER JOIN [DBO].[LOCATION] AS [Extent4] ON [Extent4].[LOCATION_CD] = [Extent3].[LOCATION_CD]
    LEFT OUTER JOIN [DBO].[LOCATION] AS [Extent5] ON [Extent5].[LOCATION_CD] = [Extent2].[ZIP_CD]
    INNER JOIN (SELECT 
[CUST_STS_HIS].[CUST_CD] AS [CUST_CD], 
[CUST_STS_HIS].[UDT_DT] AS [UDT_DT], 
[CUST_STS_HIS].[REASON_CD] AS [REASON_CD], 
[CUST_STS_HIS].[CUST_STS_CD] AS [CUST_STS_CD], 
[CUST_STS_HIS].[USR_ID] AS [USR_ID], 
[CUST_STS_HIS].[NOTES] AS [NOTES]
FROM [DBO].[CUST_STS_HIS] AS [CUST_STS_HIS]) AS [Extent6] ON [Extent6].[CUST_STS_CD] = [Extent1].[CUST_STS_CD]
    WHERE (cast(5 as decimal(18)) = [Extent1].[CUST_STS_CD]) AND (cast(5 as decimal(18)) = [Extent6].[CUST_STS_CD]) ) AS [Filter1]
INNER JOIN (SELECT 
[CUST_STS_REASON].[STS_CD] AS [STS_CD], 
[CUST_STS_REASON].[REASON_CD] AS [REASON_CD], 
[CUST_STS_REASON].[DSC] AS [DSC], 
[CUST_STS_REASON].[RES_KEY] AS [RES_KEY]
FROM [DBO].[CUST_STS_REASON] AS [CUST_STS_REASON]) AS [Extent7] ON [Extent7].[STS_CD] = [Filter1].[CUST_STS_CD1]

我按预期获得了我的 SQL 查询结果（大约 300 条左右的记录）。但是，我的 lambda 带来了所有记录（超过 100k）。完全忽略我在声明中的“where”子句。您能否在此查询中指出正确的方向？感谢您的时间和考虑。

【问题讨论】：

A.ADDR_CD = 5 去哪儿了？
你可以随时查看EF生成的sql是什么，看看有什么区别。检查这个答案stackoverflow.com/questions/1412863/…
这是哪个 ORM - EF Core？哪个版本？
@GuillaumeCR - 它是这样的“来自 b”：from b in db.RET_ADDR .Where(bb => bb.RET_CD == a.RET_CD && bb.ADDR_CD == 5) .仍然带来大约 76k 条记录
@IvanStoev - 这来自 EF6。

标签： sql linq lambda

【解决方案1】：

好吧，既然给猫剥皮的方法不止一种，我最终创建并执行了一个存储过程，它解决了问题并只返回了我需要的数据。不过，感谢您的所有回复。我真的在这里学到了一些新东西。我很感激！

【讨论】：