Question

我想知道Linq和SQL是否相等（意味着Linq将返回与SQL相同的结果集？我没有表中的数据，我需要将SQL转换为LINQ。请建议

 var excludeTypes = new[]
               {
                  "CA00", "CA01", "CA03", "CA04", "CA02",
                  "PA00", "PA01", "PA02", "PA03", "PA04"     
               };

 var accounts =
                from account in context.Accounts
                from owner in context.AccountOwners
                from business in context.Businesses
                from accountStatus in context.AccountStatuses
                from legalStatus in context.LegalStatuses
                where !excludeTypes.Contains(account.AccountType)
                select new AccountsReport { Account = account };


 ALTER VIEW [dbo].[vwRptBorrowerAccount]  
AS  
SELECT dbo.tblAccount.[Creditor Registry ID], dbo.tblAccount.[Account No], dbo.tblAccount.[Date Opened], dbo.tblAccount.[Account Status ID],   
               dbo.tblAccount.[Date First Reported], dbo.tblAccount.[Credit Limit], dbo.tblAccount.Balance, dbo.tblAccount.[Minimum Installment], dbo.tblAccount.[Account Type],   
               dbo.tblAccount.Term, dbo.tblAccount.Purpose, dbo.tblAccount.[Account Owner Notes], dbo.tblAccount.[Creditor Notes], dbo.tblAccount.Collateral,   
               dbo.tblAccount.[Collateral Value], dbo.tblAccount.[Legal Status ID], dbo.tblAccount.[Legal Status Date], dbo.tblAccount.LastUpdatedBy,   
               dbo.tblAccount.LastUpdated, dbo.tblAccount.[Unique ID], dbo.tblAccount.[Account Status Date], dbo.tblAccount.Payment, dbo.tblAccount.[Payment Date],   
               dbo.tblAccount.[Balance Date], dbo.tblAccount.[Term Frequency], dbo.tblAccount.[State Change Date],   
               dbo.fn_GetAccountTypeDescription(dbo.tblAccount.[Account Type]) AS [Account Type Description], dbo.tblBusiness.[Business Name] AS CreditorName,   
               dbo.tblBusiness.Address AS CreditorAddress, dbo.tblBusiness.City AS CreditorCity, dbo.tblBusiness.State AS CreditorState,   
               dbo.tblLegalStatus.[Legal Status Description] AS [Legal Status], dbo.tblAccountStatus.[Account Status Description] AS [Account Status],   
               dbo.tblAccountOwner.[Account Owner Registry ID]  
FROM  dbo.tblAccount INNER JOIN  
               dbo.tblAccountOwner ON dbo.tblAccount.[Creditor Registry ID] = dbo.tblAccountOwner.[Creditor Registry ID] AND   
               dbo.tblAccount.[Account No] = dbo.tblAccountOwner.[Account No] INNER JOIN  
               dbo.tblBusiness ON dbo.tblAccount.[Creditor Registry ID] = dbo.tblBusiness.[Registry ID] INNER JOIN  
               dbo.tblAccountStatus ON dbo.tblAccount.[Account Status ID] = dbo.tblAccountStatus.[Account Status ID] INNER JOIN  
               dbo.tblLegalStatus ON dbo.tblAccount.[Legal Status ID] = dbo.tblLegalStatus.[Legal Status ID]  
WHERE (dbo.tblAccount.[Account Type] NOT IN ('CA00', 'CA01', 'CA03', 'CA04', 'CA02', 'PA00', 'PA01', 'PA02', 'PA03', 'PA04'))

Answer 1

不，你的linq不等同于你的sql。你错过了表之间的关系。

第二个和第三个“来自”被转换为对System.Linq.Queryable.SelectMany的调用。由于没有指定关系，因此该查询将每个帐户与每个AccountOwner匹配，然后每个结果对与每个Business匹配。这被称为笛卡尔联合（所有可能的匹配）。

from account in context.Accounts
from owner in context.AccountOwners
from business in context.Businesses

更传统的方法是在查询中指定关系。此查询将每个帐户与其AccountOwner匹配，然后每个帐户都与其业务匹配。这称为内连接。（注意，必须使用关键字equals。另请注意严格的范围规则on (leftside) equals (rightside)）。

from account in context.Accounts
join owner in context.AccountOwners
  on new {account.RegistryId, account.AccountNo}
  equals new {owner.RegistryId, owner.AccountNo}
join business in context.Businesses
  on account.CreditorRegistryID
  equals business.RegistryID

第二个和第三个“来自”被转换为对System.Linq.Queryable.SelectMany的调用。由于存在指定的关系，因此该查询将每个帐户与其AccountOwners及其企业进行匹配。这是一个内部联接（Account = 1，其他=很多）。

from account in context.Accounts
from owner in account.AccountOwners
from business in account.Businesses

此查询将每个帐户与其唯一的AccountOwner及其唯一的Business.This匹配。这也是内部联接（Account = Many，其他= 1）。

from account in context.Accounts
let owner = account.AccountOwner
let business = account.Business

Linq查询更正

1 个答案: