子查詢中LAMBDA

Question

我越來越

這裏是我的SQL Server的查詢，而我試圖轉換成

select * from Permission Where PermissionId in(select PermissionId from RoleDetail where RoleId =1) 

這裏是我最初的拉姆達子查詢

from p in Permissions 
    let rde = from rd in RoleDetails 
     select rd.PermissionId 
     where p.PermissionId ==1 
     select p 

但其表現我只有一個記錄附有該角色，但實際上它有5個權限請幫助。

Answer 1

也許嘗試呢？而不是試圖用.Contains()，只是做在兩個表加入...

from p in Permissions 
join rd in RoleDetails on p.PermissionId equals rd.PermissionId 
where rd.RoleId == 1 
select p; 

Answer 2

使用Join： -

var result = from p in Permissions 
      join rd in RoleDetails.Where(x => x.RoleId == 1) 
      on p.PermissionId equals rd.PermissionId 
      select p; 

Answer 3

你做錯了這樣做：

from p in Permissions 
    let rde = (from rd in RoleDetails 
       where rd.RoleId ==1 
       select rd.PermissionId) 
where p.PermissionId = rde 
select p 

見LET usage HERE

Answer 4

使用連接（在其他的建議swers）是更好的，但解決您的查詢，您應該過濾rde上RoleId = 1然後過濾Permissions與rde：

from p in Permissions 
    let rde = from rd in RoleDetails 
     where rd.RoleId == 1   // filter RoleId = 1 
     select rd.PermissionId 
    where rde.Contains(p.PermissionId) // rde should contain p.PermissionId 
    select p