Linq left outer join 和 union 返回许多记录

Question

我正在将一个运行良好的存储过程转换为 linq 查询，但没有得到正确的记录。存储过程如下所示：

SELECT isnull(a.CertificationId, cc.CertificationId) as CertificationId, 
    isnull(a.cipcode, cc.CipCode) as CipCode,isnull(a.Credential, lc.Credential) as Credential, 
    lc.LicensingCertificationProgram, lc.IssuingOrganization, isnull(a.ab, '') as ab
FROM     enrCertificationCipCodes CC INNER JOIN
     lkpCertifications lc ON CC.CertificationId = lc.CertificationId 
     left join
        (SELECT pc.CertificationId, 
        cc.CipCode, 
        lc.Credential, 
        lc.LicensingCertificationProgram, 
        lc.IssuingOrganization, ab = 'Yes',
        pc.psn
            FROM     enrCertificationCipCodes CC INNER JOIN
            lkpCertifications lc ON CC.CertificationId = lc.CertificationId
            inner join (select * from enrProgramCertifications where PSN = @PSN) PC on cc.CertificationId = pc.CertificationId ) as a on a.CertificationId = cc.CertificationId 
where cc.CipCode = @CipCode 
union
select pc.CertificationId as CertificationId, p.cipcode as CipCode, other as Credential,'' as LicensingCertificationProgram, 
   '' as IssuingOrganization, 'Yes' as ab
 from (select * from enrProgramCertifications where CertificationId  = '99999') pc join enrProgram p on pc.PSN = p.PSN 
  where p.CIPCode = @CipCode and p.PSN = @PSN
  Union
select '99999' as CertificationId, @CipCode as CipCode, 'Other' as Credential,'' as LicensingCertificationProgram, '' as IssuingOrganization, '' as ab
order by ab desc, Credential

我的 linq 查询是

var t = ((from a in LkpCertifications 
        join d in EnrProgramCertifications on a.CertificationId equals d.CertificationId into ad
                 from d in ad.DefaultIfEmpty()
                 join c in EnrCertificationCipCodes on a.CertificationId equals c.CertificationId
                 where c.CipCode == "52.1999"
                 select new {
                 CertificationId = a.CertificationId,
                 CipCode = c.CipCode,
                 Credential = a.Credential,
                 Licensing = a.LicensingCertificationProgram,
                 IssuingOrganization = a.IssuingOrganization,
                 Psn = d.PSN != null ? d.PSN : 0,
                 ab = d.PSN != null ? "Yes" : ""
                 })
                 .Union (from k in EnrProgramCertifications
                 join l in LkpCertifications on k.CertificationId equals l.CertificationId where k.PSN == 19480
                 select new{
                 CertificationId = k.CertificationId,
                 CipCode = "52.1999",
                 Credential = k.Other,
                 Licensing = l.LicensingCertificationProgram,
                 IssuingOrganization = l.IssuingOrganization,
                 Psn = k.PSN != null ? k.PSN : 0,
                 ab = k.PSN != null ? "Yes" : ""
                 })).ToList();

t.Dump();

结果是我从左侧加入了更多行 table。如果我尝试通过使用 PSN 号码限定它来限制从左侧加入 table 的行，那么我不会从 lkpCertifications table 获得结果。 lkpCertifications 包含所有证书，而 enrProgramCertifications 仅包含那些已被选中的证书，就像订单和订单详细信息设置一样。

所以我目前的结果看起来像

我应该只得到一个 PSN 为 0 的项目 54 和一个 PSN 为 19480 的 55 记录。

对这个问题有什么想法吗？

Answer 1

我能够通过使用一对连接到对象中来解决这个问题，这些对象 defaultifempty() 到 return 左外连接。

                certs = (from a in _context.LkpCertifications
                     join d in _context.EnrProgramCertifications on a.CertificationId equals d.CertificationId into ad
                     from d in ad.DefaultIfEmpty()
                     join c in _context.EnrCertificationCipCodes on a.CertificationId equals c.CertificationId into ac
                     from c in ac.DefaultIfEmpty()
                     where c.CipCode == CIP || d.Psn == Psn
                     select new vmManageCertifications
                         {
                         Psn = d.Psn == Psn ? d.Psn : 0,
                         Cipcode = c.CipCode == null ? "0" : c.CipCode,
                         CertificationId = a.CertificationId,
                         Credential = a.Credential == "Other" ? d.Other : a.Credential,
                         LicensingCertificationProgram = a.LicensingCertificationProgram,
                         IssuingOrganization = a.IssuingOrganization,
                         ProgramCertified = d.Psn == Psn ? true : false
                         }).ToList().GroupBy(i => i.CertificationId).Select(group => group.First()).OrderByDescending(i => i.ProgramCertified);

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