Sql 从表中选择第一个id

我想根据我的子类别列出所有条目。所以我想在加载主页上显示条目列表，而不必事先选择任何类别或子类别

我做了一个查询，返回条目列表，但手动放置子类别ID

以下是查询：

 int userId = WebSecurity.GetUserId(User.Identity.Name);

  var preQuery = (from sub in dc.SubCategory
                  join c in dc.Category on sub.SubCategoryId equals c.Id
                  join u in dc.User on c.UserId equals u.UserId
                  where u.UserId == userId
                  select sub.SubCategoryId).Take(1).FirstOrDefault();

        var query = (from e in dc.Entry
                     join sub in dc.SubCategory on e.SubCategoryId equals sub.SubCategoryId
                     join cat in dc.Category on sub.CategoryId equals cat.Id
                     join u in dc.User on cat.UserId equals u.UserId
                     where ((u.UserId == userId) && (cat.UserId == userId) 
                         && (sub.CategoryId == cat.Id) && (e.SubCategoryId == preQuery ))
                     select e).ToList();

        return View(query);

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因此，我的观点是，我不想手动写入id 6，而是希望获取子类别id列表并从中选择第一个id。我已经进行了预查询，但仍然没有得到所需的结果。有任何建议说明我做错了什么吗？

我能够为我的问题找到解决方案，因此我发布了解决方案。如果任何人有优化解决方案的建议，欢迎分享

  int userId = WebSecurity.GetUserId(User.Identity.Name);

        var preQuery = (from e in dc.Entry
                     join sub in dc.SubCategory on e.SubCategoryId equals sub.SubCategoryId
                     join cat in dc.Category on sub.CategoryId equals cat.Id
                     join u in dc.User on cat.UserId equals u.UserId
                     where u.UserId == userId
                     select e.SubCategoryId).Take(1);

        var query = (from e in dc.Entry
                     join sub in dc.SubCategory on e.SubCategoryId equals sub.SubCategoryId
                     join cat in dc.Category on sub.CategoryId equals cat.Id
                     join u in dc.User on cat.UserId equals u.UserId
                     where ((u.UserId == userId) && (cat.UserId == userId)
                         && (sub.CategoryId == cat.Id) && (e.SubCategoryId == preQuery.FirstOrDefault()))
                     select e).ToList();

        return View(query);

---

无论出于什么原因，您为什么不想进行预查询，在其中您将选择firs ID。这可能是您进行预查询的最快选项，但仍然不是所需的结果。建议我做错了什么？尝试使用Let