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以下のSQLをLINQクエリに変換するのに行き詰まっています。基本的には、テーブルの成績で試験をグループ化し、合格、不合格、受験回数、合格率の合計を計算したいだけです

SELECT testID, 
(SELECT COUNT(testID) FROM tblGrade AS b 
    WHERE b.testID= a.testID AND b.Grade < 80) AS 'Failed',
(SELECT COUNT(testID) FROM tblGrade AS b 
    WHERE b.testID= a.testIDAND b.Grade >= 80) AS 'Passed',
--taken = failed + passed, 
--passingrate = (passed / taken) * 100
FROM dbo.tblGrade AS a
GROUP BY testID
ORDER BY testID

編集:以下の私の解決策:それは機能しますが、特に失敗したプロパティと渡されたプロパティが最善の方法ではないと思います。

var xx1 = _unitOfWork.tblGrade.GetAll().GroupBy(a => new { a.testID});
var xx2 = xx1.Select(b => new
           {
             testID= b.Key.testID,
             failed = _unitOfWork.tblGrade.Query(filter: a => a.testID == b.Key.testID).Where(c => c.Grade < 80).Count(),
             passed = _unitOfWork.tblGrade.Query(filter: a => a.testID == b.Key.testID).Where(c => c.Grade >= 80).Count(),
             //taken = failed + passed, 
             //passingrate = (passed / taken) * 100
            }).ToList();
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2 に答える 2

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Count()述語 ( ) を引数として取ることができるExpression<Func<T, bool>>ので、そのままでよいと思います

var xx2 = xx1.Select(b => new
           {
             testID= b.Key.testID,
             failed = b.Count(x => x.Grade < 80),
             passed = b.Count(x => x.Grade >=80),
             taken = b.Count()
            })
            .Select(b => new {
               testID = b.TestID,
               failed = b.failed,
               passed = b.passed,
               taken = b.taken,
               passingrate = b.taken == 0 ? 0.0 : ((float)b.passed / b.taken) * 100
            }).ToList();

クエリ構文には (この場合に役立つ)letキーワードがあるため、読みやすいかもしれません

var xx2 = from b in xx1
          let failed = b.Count(x => x.Grade < 80)
          let passed = b.Count(x => x.Grade >= 80)
          let taken = failed + passed
          select new {
              testID = b.Key.TextID,
              failed = failed,
              passed = passed,
              taken = taken,
              passingrate = taken == 0 ? 0.0 : ((float)passed / taken) * 100
          }
于 2013-07-30T12:07:11.377 に答える
0

これは私がそれを行う方法です：

  var h = list.GroupBy(a => a.testID)
            .Select(a => {
               int _failed = a.Count(g => g.Grade < 80);
               int _passed = a.Count(g => g.Grade >= 80);
               int _rate = (int)(_passed / (double)a.Count() * 100.0);

               return new {
                 testID = a.Key,
                 failed = _failed,
                 passed = _passed,
                 taken = a.Count(),
                 rate = _rate,
              };     
            });

完全なテスト コード:

void Main()
{
  List<aGrade> list = new List<aGrade>() {
    new aGrade() { Grade = 40, testID = 1 },
    new aGrade() { Grade = 50, testID = 1 },
    new aGrade() { Grade = 45, testID = 1 },
    new aGrade() { Grade = 70, testID = 1 },
    new aGrade() { Grade = 80, testID = 1 },
    new aGrade() { Grade = 90, testID = 1 },
    new aGrade() { Grade = 40, testID = 2 },
    new aGrade() { Grade = 50, testID = 2 },
    new aGrade() { Grade = 45, testID = 2 },
    new aGrade() { Grade = 70, testID = 2 },
    new aGrade() { Grade = 80, testID = 2 },
    new aGrade() { Grade = 90, testID = 2 },
    new aGrade() { Grade = 40, testID = 3 },
    new aGrade() { Grade = 50, testID = 3 },
    new aGrade() { Grade = 45, testID = 3 },
    new aGrade() { Grade = 70, testID = 3 },
    new aGrade() { Grade = 80, testID = 3 },
    new aGrade() { Grade = 90, testID = 3 },
  };    

  var h = list.GroupBy(a => a.testID)
            .Select(a => {
               int _failed = a.Count(g => g.Grade < 80);
               int _passed = a.Count(g => g.Grade >= 80);
               int _rate = (int)(_passed / (double)a.Count() * 100.0);

               return new {
                 testID = a.Key,
                 failed = _failed,
                 passed = _passed,
                 taken = a.Count(),
                 rate = _rate,
              };     
            }); 
  h.Dump(); 
}
// Define other methods and classes here

public class aGrade
{
    public int Grade {  get; set; }
    public int testID { get; set; }
}

注意 - このコードは、LinqPad と同じように機能します。(linqpad.com) この種のコードのテストには linqpad をお勧めします...作業がとても簡単になります。それを試してみてください。

于 2013-07-30T14:46:09.863 に答える