我应该在 msdb 中删除 MS_DataCollectorInternalUser 吗？

MS_DataCollectorInternalUser不是孤立用户。是没有登录的用户，另类的野兽。我建议您更新您的安全实践，您可能已经删除了其他有效的非孤立用户。除非您有特定的安全公告引用删除或修改此用户的理由，否则您应该保留它。

我找不到来自 Microsoft 网站的参考，但根据Alfred Songy的博客文章。 MS_DataCollectorInternalUser与数据收集器有关。它是故意创建的没有 SQL 登录的用户帐户，并且没有登录创建的用户显然无法连接到数据库，因此我没有看到安全风险。我的建议是不应该删除删除，修改系统数据库中的任何内容不是一个好主意。:)

下面的这个查询有助于识别孤立的 SQL Server 用户。

select DB_NAME() [database], name as [user_name], type_desc,default_schema_name,create_date,modify_date from sys.database_principals 
where type in ('G','S','U') 
and authentication_type<>2 -- Use this filter only if you are running on SQL Server 2012 and major versions and you have "contained databases"
and [sid] not in ( select [sid] from sys.server_principals where type in ('G','S','U') ) 
and name not in ('dbo','guest','INFORMATION_SCHEMA','sys','MS_DataCollectorInternalUser')

在我们知道我们将删除哪些用户之后，考虑到需要首先删除与模式和数据库角色的关联，可以使用以下脚本删除孤立用户。

use [master]
go
create proc dbo.sp_Drop_OrphanedUsers
as
begin
 set nocount on
 -- get orphaned users  
 declare @user varchar(max) 
 declare c_orphaned_user cursor for 
  select name
  from sys.database_principals 
  where type in ('G','S','U') 
  and authentication_type<>2 -- Use this filter only if you are running on SQL Server 2012 and major versions and you have "contained databases"
  and [sid] not in ( select [sid] from sys.server_principals where type in ('G','S','U') ) 
  and name not in ('dbo','guest','INFORMATION_SCHEMA','sys','MS_DataCollectorInternalUser')  open c_orphaned_user 
 fetch next from c_orphaned_user into @user
 while(@@FETCH_STATUS=0)
 begin
  -- alter schemas for user 
  declare @schema_name varchar(max) 
  declare c_schema cursor for 
   select name from  sys.schemas where USER_NAME(principal_id)=@user
  open c_schema 
  fetch next from c_schema into @schema_name
  while (@@FETCH_STATUS=0)
  begin
   declare @sql_schema varchar(max)
   select @sql_schema='ALTER AUTHORIZATION ON SCHEMA::['+@schema_name+ '] TO [dbo]'
   print @sql_schema
   exec(@sql_schema)
   fetch next from c_schema into @schema_name
  end
  close c_schema
  deallocate c_schema   

  -- alter roles for user 
  declare @dp_name varchar(max) 
  declare c_database_principal cursor for 
   select name from sys.database_principals
   where type='R' and user_name(owning_principal_id)=@user
  open c_database_principal
  fetch next from c_database_principal into @dp_name
  while (@@FETCH_STATUS=0)
  begin
   declare @sql_database_principal  varchar(max)
   select @sql_database_principal ='ALTER AUTHORIZATION ON ROLE::['+@dp_name+ '] TO [dbo]'
   print @sql_database_principal 
   exec(@sql_database_principal )
   fetch next from c_database_principal into @dp_name
  end
  close c_database_principal
  deallocate c_database_principal

  -- drop roles for user 
  declare @role_name varchar(max) 
  declare c_role cursor for 
   select dp.name--,USER_NAME(member_principal_id)
   from sys.database_role_members drm
   inner join sys.database_principals dp 
   on dp.principal_id= drm.role_principal_id
   where USER_NAME(member_principal_id)=@user 
  open c_role 
  fetch next from c_role into @role_name
  while (@@FETCH_STATUS=0)
  begin
   declare @sql_role varchar(max)
   select @sql_role='EXEC sp_droprolemember N'''+@role_name+''', N'''+@user+''''
   print @sql_role
   exec (@sql_role)
   fetch next from c_role into @role_name
  end
  close c_role
  deallocate c_role   

  -- drop user
  declare @sql_user varchar(max)
  set @sql_user='DROP USER ['+@user +']'
  print @sql_user
  exec (@sql_user)
  fetch next from c_orphaned_user into @user
 end
 close c_orphaned_user
 deallocate c_orphaned_user
 set nocount off
end
go
-- mark stored procedure as a system stored procedure
exec sys.sp_MS_marksystemobject sp_Drop_OrphanedUsers
go

以下是对 SQL Server 实例中的所有数据库执行它的方法：

USE [master]
GO
EXEC sp_msforeachdb 'USE [?]; EXEC sp_Drop_OrphanedUsers'

另一个有用的链接可以解决您的问题

希望我的回答有帮助！