Sql 如果不存在，请选择一些数据

我编写了一个从tbl中选择最高记录的查询。我想检查tbl中是否没有记录我的查询返回假数据，如（StudentId=1，HighScore=0）

试试这个：

var queryWin = (from T in ((from tbl_ActPoints in dc.tbl_ActPoints
                select new
                {
                    tbl_ActPoints.StudentId,
                    tbl_ActPoints.Score
                }))
    group T by new
    {
        T.StudentId
    } into g
    orderby
      ((System.Int32?)g.Sum(p => p.Score) ?? (System.Int32?)0) descending
    select new
    {
        g.Key.StudentId,
        HighScore = ((System.Int32?)g.Sum(p => p.Score) ?? (System.Int32?)0)
    }).Take(1);

var result = queryWin.FirstOrDefault();

if (result == null)
  result = new { StudentId = 1, HighScore=0 };

---

稍微清理一下代码：

var queryWin = (from tbl_ActPoints in dc.tbl_ActPoints
                group new
                {
                    tbl_ActPoints.StudentId,
                    tbl_ActPoints.Score
                } by tbl_ActPoints.StudentId into g
                orderby
                  (g.Sum(p => p.Score) ?? 0) descending
                select new StudentHighScore
                {
                    g.Key.StudentId,
                    HighScore = (g.Sum(p => p.Score) ?? 0)
                }).FirstOrDefault() 
                     ?? new StudentHighScore { StudentID = 1, HighScore = 0};

技巧，以及coolswastik代码不起作用的原因，因为两个匿名对象，即使具有相同的属性，也总是不同的，所以您需要一个命名类：

class StudentHighScore
{
    public int StudentId { get; set; }
    public int HighScore { get; set; }
}

---

编辑了答案

class StudentHighScore
{
    public int StudentId { get; set; }
    public int HighScore { get; set; }
}