m developing forums app on ASP.net ,Sql Server2008, it is on completetion level but i m getting a small problem that i've forgoten the sqlQuery for deleting the post ,,

Thnx Mika ,Wel The Same Query I've Already tried but its not working...Let me tell you further that i m using grid view to show all posts of the asked question below that question , i 've inserted a linkbutton in templete editor and neme it "delete" im giving command arument to evaluate the post id i-e Eval("post_id"), on the click of that linkbutton ,i m giving a defination of function, function code is given below...

for Binding gridview the code is:
string query2 = @"SELECT userTB.user_id, userTB.user_name, userTB.user_contact, userTB.user_country, userTB.user_city, userTB.user_proffesion, userTB.user_pic, postTB.post, postTB.post_id, postTB.question_id, postTB.user_id AS Expr1, postTB.postdate FROM postTB INNER JOIN userTB ON postTB.user_id = userTB.user_id where postTB.question_id='"+Application["question_id"]+"'";
SqlDataAdapter da2 = new SqlDataAdapter(query2, con);
DataSet ds2 = new DataSet();
da2.Fill(ds2);
GridView2.DataSource = ds2;
GridView2.DataBind();

and for the linkbutton_click:


protected void LinkButton8_Click(object sender, EventArgs e)
{
LinkButton lnk = (LinkButton)sender;
Application["post_id"]= lnk.CommandArgument;
SqlConnection con = new SqlConnection(_cs);
con.Open();
SqlCommand cmd1 = new SqlCommand("delete from postTB where post_id = '"+lnk.CommandArgument+"' AND user_id ='"+Application["user_id"]+"' ",con);

cmd1.ExecuteNonQuery();
con.Close();
}


prob is that the records are shown correctly but when i click the linkButton (Delete) in gridview then the record button then all records can be deleted,,,,which is not required,,,, the only record of the login user must be delted,,, plz Help ...Thnx