sqldataadapter not displaying all the record in detailview

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C#

ASP.NET

SQL-Server

, +

i have 3 table namely USERS, Groups, and Student

private bool BindData(string query)
    {
        try
        {
            String connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ToString();
            SqlConnection con = new SqlConnection(connectionString);            
            SqlDataAdapter adapter = new SqlDataAdapter(query, con);
            DataSet ds = new DataSet();
            adapter.Fill(ds);            
            studentDetailsView.DataSource = ds;            
            studentDetailsView.DataBind();
            return true;
        }
        catch
        {
            return false;
        }
    }

the adapter.fill(ds) displays the correct result is shown when debugged but when its time to show in detailview it only displays first record of student against selected group

please suggest me how to display all the student data against selected group.
i have used this to display the data

<asp:DetailsView><asp:TemplateField HeaderText="LoginID">
                    <ItemTemplate>
                        <asp:Literal ID="litLoginID" runat="server" Text=' <%# Eval("LoginID")  %> ' />
                    </ItemTemplate>
                </asp:TemplateField>

and displayed all the info that is returned by the query