通过一个表的字段向令一个表更新字段

[zilong4460072]

表的字段: room(roomnumb,price,entrydays,staydays,empty)
yuding(roomnumb,entrydays,staydays)
把表yuding绑定到Grid View1上后
用RowCommand怎么样把预定表的entrydays,staydays的字段更新到room表里(room与yuding的roomnumb字段是同一个)
我在Grid View1添加了BUtton按钮 ，RowCommand事件代码 ：

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
int index = Convert.ToInt32(e.CommandArgument);
string roomnumb=GridView1.DataKeys[index].Value.ToString();

string strconnection=ConfigurationManager.ConnectionStrings["123"].ConnectionString;
SqlConnection conn = new SqlConnection(strconnection);
string sql = "set select * from yuding where roomnumb='"+roomnumb+"'" ;
SqlCommand cmd = new SqlCommand(sql,conn);
cmd.ExecuteReader();
conn.Open();
}

不知道应该怎样来写代码!

[jiang_jiajia10]

update table set roomnumb = (select * from yuding where roomnumb='"+roomnumb+"')

[一弗楚]

string sql=string.Format("update room set entrydays='{0}',staydays='{1}' where roomnumb='{2}'",当前列行entrydays值，当前列行staydays值，当前列行roomnumb值）

[wuyq11]

通过 select * from yuding where roomnumb='"+roomnumb+"'
先查询entrydays,staydays
再执行update room set entrydays='',staydays=''where roomnumb='"+roomnumb+"'

[criedshy]

设置DataKeyNames="roomnumb,entrydays,staydays"

<asp:GridView ID="GridView1" runat="server"  AllowSorting="True"  DataKeyNames="roomnumb,entrydays,staydays"  OnRowCommand="GridView1_RowCommand"/>

<asp:TemplateField HeaderText="修改">
                   <ItemTemplate>
                     <asp:Button ID="btnPLC" Text="修改"  CommandName="update" CommandArgument="<%# ((GridViewRow)Container).RowIndex %>" runat="server" />
                   </ItemTemplate>
                </asp:TemplateField>

后台代码

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
    {
        if (e.CommandName == "update")
        {
           int index = Convert.ToInt32(e.CommandArgument); 
           string roomnumb=GridView1.DataKeys[index].Values["roomnumb"].ToString(); 
           string entrydays=GridView1.DataKeys[index].Values["entrydays"].ToString(); 
           string staydays=GridView1.DataKeys[index].Values["staydays"].ToString(); 
        string strconnection=ConfigurationManager.ConnectionStrings["123"].ConnectionString; 
        SqlConnection conn = new SqlConnection(strconnection); 
        conn.Open();
        string sql = "update room set staydays='"+staydays+"',entrydays='"+entrydays+"' where  roomnumb="+roomnumb; 
        SqlCommand cmd = new SqlCommand(sql,conn); 
        cmd.ExecuteNonQuery(); 
        conn.Close();
         

        }
}

[qinhl99]

up