ถามเกี่ยวกับ Group by ใน sql server ค่ะ สวัสดีค่ะ คือต้องการ หาผลรวมของปริมาณเลือดแต่ละหมู่ค่ะ

<%@ Import Namespace="System.Data"%>
<%@ Import Namespace="System.Data.SqlClient"%>
<%@Import Namespace="System.IO" %>
<%@ Page Language="VB" %>

<%@ Register Assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
    Namespace="System.Web.UI" TagPrefix="asp" %>
<script runat="server">

    Dim objConn As SqlConnection
    Dim objCmd As SqlCommand

    Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
        Dim strConnString As String
        strConnString = "Server=localhost;UID=sa;PASSWORD=xxxx;database=blooddb;Max Pool Size=400;Connect Timeout=600;"
        objConn = New SqlConnection(strConnString)
        objConn.Open()
        BindData()
        Label2.Text = "Last update :" + " " + DateTime.Now.ToString()
    End Sub
    
   
    Sub IntervalTimer_Tick(ByVal sender As Object, ByVal e As EventArgs) Handles IntervalTimer.Tick
        
        Label2.Text = "Last update :" + " " + DateTime.Now.ToString()
        BindData()
    End Sub
   
    Sub BindData()
       
		Dim ds As DataSet
		ds = CreateDataSet()
		myRepeater.DataSource = ds.Tables(0).DefaultView
		myRepeater.DataBind()	

    End Sub
     
	Function CreateDataSet() As DataSet

        Dim objConn As New System.Data.SqlClient.SqlConnection
		Dim objCmd As New System.Data.SqlClient.SqlCommand
        Dim dtAdapter As New System.Data.SqlClient.SqlDataAdapter
        Dim wr As StreamWriter = File.CreateText(Server.MapPath("computeblood.xml"))
		
        Dim ds As New DataSet
		Dim strConnString,strSQL As String


        strConnString = "Server=localhost;UID=sa;PASSWORD=xxxx;database=blooddb;Max Pool Size=400;Connect Timeout=1000;"
        strSQL = "SELECT BloodGroup,SUM(Quantity) FROM CallEmerge GROUP BY BloodGroup"
        
		objConn.ConnectionString = strConnString
		With objCmd
			.Connection = objConn
			.CommandText = strSQL			
			.CommandType = CommandType.Text
		End With
		dtAdapter.SelectCommand = objCmd

		dtAdapter.Fill(ds)

        '***ds.WriteXml(Server.MapPath("computeblood.xml"))***'		
		ds.WriteXml(wr)
		wr.Close()
		
		dtAdapter = Nothing
		
		objConn.Close()
		objConn = Nothing
		
		Return ds   '*** Return DataSet ***'
		
	End Function
</script>

strSQL = "SELECT BloodGroup,Quantity FROM CallEmerge GROUP BY BloodGroup,Quantity"