在asp.net中找不到我的查询错误

我在gridview的每一行都有一个gridview和链接按钮。当我单击其中一个按钮时，我会得到此行的courseName、courseCode和term列值。这是我的密码：

 int row = -1;
        int.TryParse(e.CommandArgument as string, out row);

        GridViewRow gdrow = instCourses.Rows[row];

        // *** Get the underlying data item - in this case a DataRow
        DataRow dr = ((DataTable)this.instCourses.DataSource).Rows[gdrow.DataItemIndex];

        // *** Retrieve our context
        string courseCode = dr["CourseCode"].ToString();
        string courseNumber = dr["CourseNumber"].ToString();
        string term = dr["Term"].ToString();
        SqlConnection con = new SqlConnection();
        con.ConnectionString = Userfunctions.GetConnectionString();
        con.Open();
        SqlCommand cmd=new SqlCommand("select RegisterTable.StudentID,StudentTable.Name,StudentTable.Surname from RegisterTable INNER JOIN StudentTable where RegisterTable.StudentID=StudentTable.StudentID and RegisterTable.CourseCode=@courseCode and RegisterTable.Term=@term and RegisterTable.CourseNumber=@courseNumber",con);
        cmd.Parameters.AddWithValue("@courseCode", courseCode);
        cmd.Parameters.AddWithValue("@courseNumber", courseNumber);
        cmd.Parameters.AddWithValue("@term", term);
        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataTable dt = new DataTable();
        da.Fill(dt);
        studList.DataSource = dt;
        studList.DataBind();

返回的值与我预期的一样，但我认为我的查询有问题，它在关键字“where”附近显示了不正确的语法。有人看到问题了吗

---

谢谢

您有一个内部连接，没有外部连接

select RegisterTable.StudentID,StudentTable.Name,StudentTable.Surname from RegisterTable INNER JOIN StudentTable ON RegisterTable.studentid = StudentTable .id  where RegisterTable.StudentID=StudentTable.StudentID and RegisterTable.CourseCode=@courseCode and RegisterTable.Term=@term and RegisterTable.CourseNumber=@courseNumber

---

你在这里缺少连接条件

FROM RegisterTable INNER JOIN StudentTable

您的内部连接应该如下所示

from RegisterTable INNER JOIN StudentTable 
   ON RegisterTable.StudentID = StudentTable.StudentId

根据where子句，可以不使用内部联接编写查询，只需使用笛卡尔积即可

select 
        RegisterTable.StudentID,
        StudentTable.Name,
        StudentTable.Surname 
from    RegisterTable, StudentTable 
where   RegisterTable.StudentID=StudentTable.StudentID and 
        RegisterTable.CourseCode=@courseCode and 
        RegisterTable.Term=@term and 
        RegisterTable.CourseNumber=@courseNumber

---

格式化sql查询，您将看到问题：

select RegisterTable.StudentID,StudentTable.Name,StudentTable.Surname 
from RegisterTable INNER JOIN StudentTable 
where RegisterTable.StudentID=StudentTable.StudentID 
and RegisterTable.CourseCode=@courseCode 
and RegisterTable.Term=@term 
and RegisterTable.CourseNumber=@courseNumber

联接中没有关于子句的

from RegisterTable INNER JOIN StudentTable 
    ON RegisterTable.StudentID=StudentTable.StudentID 
where ....

顺便说一下，在C#中，您可以使用逐字记录来格式化sql：

string sql = @"
    SELECT registertable.studentid, 
           studenttable.name, 
           studenttable.surname 
    FROM   registertable 
           INNER JOIN studenttable 
                   ON registertable.studentid = studenttable.studentid 
    WHERE  registertable.coursecode = @courseCode 
           AND registertable.term = @term 
           AND registertable.coursenumber = @courseNumber";

这样就更容易在sql查询中找到错误。
查询语法不正确。尝试：

SELECT 
    RegisterTable.StudentID,
    StudentTable.Name,
    StudentTable.Surname 
FROM RegisterTable 
INNER JOIN StudentTable ON RegisterTable.StudentID = StudentTable.StudentID
WHERE 
    RegisterTable.CourseCode = @courseCode 
    AND RegisterTable.Term = @term 
    AND RegisterTable.CourseNumber = @courseNumber

您需要将
WHERE
更改为
ON
以完成
连接
，然后您应该将其余条件移动到
WHERE
子句。
您需要使用
ON
而不是
WHERE
指定每个表中要连接的
StudentTable
列：

SELECT RegisterTable.StudentID, StudentTable.Name, StudentTable.Surname
FROM RegisterTable
INNER JOIN StudentTable ON RegisterTable.StudentID = StudentTable.StudentID
WHERE RegisterTable.CourseCode = @courseCode
    AND RegisterTable.Term = @term
    AND RegisterTable.CourseNumber = @courseNumber

在那个SQL语句中，您只需要一个
=
。谢谢，这是有效的。唯一有效的是student表中的列的名称是ID，而不是StudentID，当我修复它时，它是有效的，谢谢！