关于update语法错误前来求学

             我有一个sum表，想让sum表中的id=1的记录的sum1(列名)+1，但是老提示我update语法错误，希望帮帮我··
             OleDbConnection conn2 = db.conn();
                conn2.Open();
                OleDbCommand cmd = new OleDbCommand("update sum set sum1=sum1+1 where id=1", conn2);
                cmd.ExecuteNonQuery();
                conn2.Close();