Select statement显示不正确的结果

Question

我实现了对我的嵌套gridview的搜索，并且All运行良好。但是当gridview加载时，它会在父表中显示重复的行。

正如你可以在图片中看到，还有AC107的CourseID下2本书。但是我的Gridview在课程中为每本教科书显示一行。我搞砸了这个选择语句，无论如何我改变它看看是否有任何工作，gridview不加载。

 protected void Page_Load(object sender, EventArgs e) 
    { 
     if (!Page.IsPostBack) 
     { 
      //i'm using a datatable for storing all the data 
      DataTable dt = new DataTable(); 
      string query = "select * from Course inner join textBooks on textBooks.CourseID = Course.CourseID"; 

      //wrapping in 'using' means the connection is closed an disposed when done 
      using (SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["HUTDMSConnectionString"].ToString())) 
      using (SqlDataAdapter adapter = new SqlDataAdapter(query, connection)) 
      { 
       try 
       { 
        //fill the datatable with the contents from the database 
        adapter.Fill(dt); 
       } 
       catch 
       { 
       } 
      } 

      //save the datatable into a viewstate for later use 
      ViewState["allBooks"] = dt; 

      GridView1.DataSource = dt; 
      GridView1.DataBind(); 
     } 
    } 

下面是我的数据表格的布局。

Answer 1

是（因为你正在使用SqlConnection提供商类假设你使用SQL Server）

SELECT * FROM (
select Course.*, 
ROW_NUMBER() OVER(PARTITION BY Course.CourseID ORDER BY Course.CourseID) AS rn 
from Course 
inner join textBooks 
on textBooks.CourseID = Course.CourseID) xxx 
WHERE rn = 1; 

你确定你的SQL查询不能取你重复的行，使用 ROW_NUMBER()功能，看看它是如何工作的像