Question

我有一个有效的SQL查询，如下所示。我想创建一个等效的Linq查询。没有太大的成功。

assemblies/except

select u.Id as userId, u.CustomerId, a.Id as appId, a.Created as appCreated from EO_AppUsers u left join EO_Policies p on (u.Id = p.AppUser_Id) CROSS APPLY ( select TOP 1 id, created, AppUser_Id from EO_Applications d WHERE d.AppUser_id = u.id order by Created desc ) a CREATE TABLE [dbo].[EO_AppUsers] ( [Id] NVARCHAR (128) NOT NULL CREATE TABLE [dbo].[EO_Policies] ( [Id] NVARCHAR (128) NOT NULL, [AppUser_Id] NVARCHAR (128) NULL, CREATE TABLE [dbo].[EO_Applications] ( [Id] NVARCHAR (128) NOT NULL, [Created] DATETIME2 (7) NOT NULL, [AppUser_Id] NVARCHAR (128) NULL,有EO_AppUsers个，零个或多个EO_Policie。

SQL会创建一份包含所有EO_Applications和相关EO_AppUsers以及最新/最新EO_Policies

的报告

以下句柄返回EO_AppUsers和EO_Policies但缺少EO_Applications。它需要上面SQL查询中的EO_Applications。

CROSS APPLY

Answer 1

您可以尝试此linq查询。

from u in EO_AppUsers
join p in EO_Policies on u.Id equals p.AppUser_Id into pl
from lp in pl.DefaultIfEmpty()  
from a in EO_Applications.Where(d => d.AppUser_Id == u.Id)
                             .OrderByDescending(d => d.Created)
                             .Take(1)
                             .DefaultIfEmpty() 
select new { userId = u.Id,
             u.CustomerId,
             appId = a.Id,
             appCreated = a.Created,
             polId = lp.Id
            }

将派生表的多表sql连接转换为Linq

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