Question

我想要检索提交表中不存在但存在于Students表中的学生姓名和学生ID，并将其绑定到GridView中。例如，A班有40名学生，但只有38名学生提交了该项目。我希望那些没有提交的学生出现在教师可以查看的GridView中

SELECT *
FROM Students
    LEFT JOIN dbo.Submission ON Students.Student_Id = Submission.Student_Id 
                                AND Students.Subject_Id = Submission.Subject_Id 
WHERE Students.Subject_Class='" + Session["Subject_Class"].ToString() + "' 
      AND Students.Subject_Id = '" + Session["Subject_Id"].ToString() + "' 
      AND  Submission.Proj_Sub = '" + Session["Proj_Sub"].ToString() + "' 
      And Submission.Student_Id IS NULL

当我使用上述语句时，GridView似乎是空的。

Answer 1

你可能想要这样的东西。

SELECT *
FROM Students
WHERE Students.Subject_Class='" + Session["Subject_Class"].ToString() + "' 
      AND Students.Subject_Id = '" + Session["Subject_Id"].ToString() + "' 
      AND NOT EXISTS (SELECT *
                      FROM Submissions
                      WHERE Submissions.Student_Id = Students.Student_Id
                            AND Submissions.Subject_Id = Students.Subject_Id
                            AND Submissions.Proj_Sub = '" + Session["Proj_Sub"].ToString() + "')

你可以采取多种方法，但这似乎是最干净的。但最重要的是，您应该重点放弃目前易于SQL注入的方法。请参数化您的查询。

使其显示在“未提交”列表中

1 个答案: