检验数据库中是否有特定记录的最简单方法

        String sqlconn = "Data Source=wei//SQLEXPRESS;Initial Catalog=HISDB;Integrated Security=True";
        SqlConnection weida = new SqlConnection(sqlconn);
        weida.Open();
        //*********************
        string sql = "SELECT tkdh FROM tkxx WHERE checked = 'True' AND tkdh='" + ckdh + "'";
    
        SqlCommand check1 = new SqlCommand(sql, weida);
      

        int j = Convert.ToInt32(check1.ExecuteScalar());
        if (j > 0) //存在
        {
            Response.Write("<script language='javascript'>alert('该出库记录已经执行退库操作,不能重复退库');</script>");  
        }
        else
        {

        }