使用 EF 实现左外连接

Question

我正在尝试在 VS2015 中使用 c# 将 sql 语句转换为 EF

下面是SQL语句：

Select i.cdin_cdindexid,p.pinv_PerformaInvID,coalesce(i.cdin_serial,0) as depno 
                         ,coalesce(convert(datetime,left(convert(nvarchar,i.cdin_startunstufdate,120),10),120),'-') as deidate,coalesce(i.cdin_goodsDesc,'-') as gooddesc ,coalesce(i.cdin_Customdeclar,'-') as custdec 
                         ,coalesce(i.cdin_NoofPackages,0) as pkg,coalesce(i.cdin_WT,0) as wt ,coalesce(i.cdin_volumewt,0) as vwt ,coalesce(i.cdin_MortgageAmount,0) as lcamt,coalesce(p.pinv_name,'-') as invno,coalesce(p.pinv_TotalAmount,0) as invamt,p.pinv_Status,p.pinv_InvoiceProperty as prop 
                         ,coalesce(c.comp_name,'-') as custname,coalesce(Comp_CompanyId,'-') as custid ,coalesce(c.comp_idcust,'-') as accpacno,coalesce(t.Terr_Caption,'-') as Terr,convert(nvarchar,'01',2) as type     
                         from cdindex i inner join   company c on i.cdin_CompanyId =c.Comp_CompanyId  inner join Territories t on i.cdin_Secterr =t.Terr_TerritoryID left outer join PerformaInv p on i.cdin_cdindexid=p.pinv_CDIndexId 
                         where(cdin_deleted Is null And c.comp_deleted Is null And t.Terr_Deleted Is null And p.pinv_deleted Is null)
                         and cdin_startunstufdate between '2016-06-01' and '2016-07-28'
                          and (p.pinv_status in('Draft','Posted') or pinv_status is null) and (p.pinv_InvoiceProperty ='01' or p.pinv_InvoiceProperty is null )

我试图实现连接，但我被困在如何使用 into 和 DefaultIfEmpty() 对 PerformaInv 表进行左外连接，然后 on i.cdin_cdindexid=p.pinv_CDIndexId

这是我尝试的：

ar q = (from i in db.CDIndexes
             join c in db.Companies on i.cdin_CompanyId equals c.Comp_CompanyId
             join t in db.Territories on i.cdin_Secterr equals t.Terr_TerritoryID into
              p from pr in p.DefaultIfEmpty

             where (i.cdin_startunstufdate>= new DateTime(2016 - 06 - 01) && i.cdin_startunstufdate>= new DateTime(2016-06-28)

             )



             select new
             {

                 i.cdin_CDIndexID,
                 i.cdin_Serial,
                 i.cdin_startunstufdate,
                 i.cdin_goodsDesc,
                 i.cdin_Customdeclar,
                 i.cdin_NoofPackages,
                 i.cdin_WT,
                 i.cdin_volumewt,
                 i.cdin_MortgageAmount,

             });

我知道缺少很多东西，但我真的很糟糕。

Answer 1

正如我在 cmets 中提到的，最好使用导航属性。但是，一旦您开始使用手动连接，将内连接转为左外连接（虽然不是自然的）就不是那么难了。

鉴于你的加入

from i in db.CDIndexes
join c in db.Companies on i.cdin_CompanyId equals c.Comp_CompanyId
join t in db.Territories on i.cdin_Secterr equals t.Terr_TerritoryID
join p in db.PerformaInvs on i.cdin_CDIndexID equals p.pinv_CDIndexId
...

您可以使用join clause (C# Reference) - Left Outer Join 中显示的模式将其中任何一个转换为左外连接

from i in db.CDIndexes
join c in db.Companies on i.cdin_CompanyId equals c.Comp_CompanyId
join t in db.Territories on i.cdin_Secterr equals t.Terr_TerritoryID
join p in db.PerformaInvs on i.cdin_CDIndexID equals p.pinv_CDIndexId
// the following line turns the above join to left outer
into p_Join from p in p_Join.DefaultIfEmpty()
...