สอบถามวิธีการเอาตัวเลขของ 2 คอลัมน์มาลบกัน แล้วเอาผลลัพธ์ที่ได้มาจัดกลุ่มครับ

select group,count(select * from tb a where (finish-start) between 0 and 100 ) as less100, count(select * from tb where (finish-start) between 101 and 200) as less200
from tb group by group

select team,count(select * from tb_job where (finish-start) between 0 and 100 ) as less100, count(select * from tb_job where (finish-start) between 101 and 200) as less200
from tb_job group by team

-- phpMyAdmin SQL Dump
-- version 2.10.3
-- http://www.phpmyadmin.net
-- 
-- Host: localhost
-- Generation Time: Jan 31, 2014 at 05:45 PM
-- Server version: 5.0.51
-- PHP Version: 5.2.6

SET SQL_MODE="NO_AUTO_VALUE_ON_ZERO";

-- 
-- Database: `test`
-- 

-- --------------------------------------------------------

-- 
-- Table structure for table `tb_job`
-- 

CREATE TABLE `tb_job` (
  `id` int(11) NOT NULL auto_increment,
  `section` varchar(2) NOT NULL,
  `team` varchar(1) NOT NULL,
  `start` varchar(4) NOT NULL,
  `finish` varchar(4) NOT NULL,
  PRIMARY KEY  (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8 AUTO_INCREMENT=10 ;

-- 
-- Dumping data for table `tb_job`
-- 

INSERT INTO `tb_job` VALUES (1, '1', 'A', '1200', '1300');
INSERT INTO `tb_job` VALUES (2, '2', 'A', '1100', '1500');
INSERT INTO `tb_job` VALUES (3, '3', 'A', '1300', '1500');
INSERT INTO `tb_job` VALUES (4, '4', 'B', '1000', '1800');
INSERT INTO `tb_job` VALUES (5, '5', 'B', '1100', '1400');
INSERT INTO `tb_job` VALUES (6, '6', 'B', '1500', '1800');
INSERT INTO `tb_job` VALUES (7, '7', 'C', '1400', '1500');
INSERT INTO `tb_job` VALUES (8, '8', 'C', '1200', '1600');
INSERT INTO `tb_job` VALUES (9, '9', 'C', '1300', '1800');

select team as t,  (select count(*) from tb_job where (finish-start) between 0 and 100 ) as less100, (select count(*) from tb_job where ((finish-start) between 101 and 200) and team = t) as less200,
(select count(*) from tb_job where ((finish-start) between 201 and 300) and team = t) as less300,
(select count(*) from tb_job where ((finish-start) > 300) and team = t) as more300
from tb_job group by team

select team as t,  (select count(*) from tb_job where ((finish-start) between 0 and 100 ) and team = t) as less100, (select count(*) from tb_job where ((finish-start) between 101 and 200) and team = t) as less200,
(select count(*) from tb_job where ((finish-start) between 201 and 300) and team = t) as less300,
(select count(*) from tb_job where ((finish-start) > 300) and team = t) as more300
from tb_job group by team