Question

我正在开发一个类似于ASP.NET网站中的简单测验引擎。我有以下数据库设计：

用户表：用户名，名称，分区代码......等

分部表：SapCode，Division

测验表：QuizID，Title，IsSent，Description

UserQuiz：UserQuizID，QuizID，DateTimeComplete，Score，Username

每周，我公司的员工都会收到一封电子邮件通知，以参与系统中可用的新测验。将发送给员工的测验将具有（True）作为IsSent属性的值，这是将其与未发送给员工的其他测验区别开来的。我现在想要的是显示上次参加测验的参与者人数，因为每周只会发送一个测验。

我的查询显示所有参加测验的参与者总数：

SELECT     dbo.Divisions.DivisionShortcut, COUNT(DISTINCT dbo.UserQuiz.Username) AS [Number of Participants], dbo.Quiz.QuizID
FROM         dbo.Divisions INNER JOIN
                      dbo.employee ON dbo.Divisions.SapCode = dbo.employee.DivisionCode INNER JOIN
                      dbo.UserQuiz ON dbo.employee.Username = dbo.UserQuiz.Username INNER JOIN
                      dbo.Quiz ON dbo.UserQuiz.QuizID = dbo.Quiz.QuizID
WHERE     (dbo.Quiz.IsSent = 1)
GROUP BY dbo.Divisions.DivisionShortcut, dbo.Quiz.QuizID

那么如何解决它只显示上次参加测验的参与者人数（发送的测验）？

Answer 1

按IsSent = 1的降序排列所有QuizID个测验，然后选择第二个排名：

;
WITH SentQuizRanked AS (
  SELECT
    *,
    ROW_NUMBER() OVER (ORDER BY QuizID DESC) AS rnk
  FROM dbo.Quiz
  WHERE IsSent = 1
)
SELECT
  d.DivisionShortcut,
  COUNT(DISTINCT uq.Username) AS [Number of Participants],
  q.QuizID
FROM dbo.Divisions d
  INNER JOIN dbo.Employee  e ON d.SapCode  = e.DivisionCode
  INNER JOIN dbo.UserQuiz uq ON e.Username = uq.Username
  INNER JOIN dbo.Quiz      q ON uq.QuizID  = q.QuizID
WHERE q.rnk = 2  /* the #1 quiz is the one being advertised,
                    so #2 is the last one taken */
GROUP BY
  d.DivisionShortcut,
  q.QuizID

如何显示上次发送/采取的测验中的参与者数量？

1 个答案: