Mysql 如何确定表中多个项目的第一个实例

标题没有很好地描述这一点，但假设Mysql 5数据库中有以下简化表：

 access

 access_id | ip        | date  | browser
 ---------------------------------------------  
 int       | char(40)  | date  | varchar(255)

我如何通过忽略NAT路由和多人从同一ip访问，以及他们的浏览器在一个日期范围内访问站点，找到确定首次用户数量的最佳方法。即：

 SELECT count(browser), browser 
   FROM access 
 WHERE date > '2011-11-1' AND date < '2011-12-1' 
 AND ip NOT IN (SELECT ip FROM access WHERE date < '2011-11-1')
 GROUP BY browser 

---

将为2011年11月之前未访问过该网站的用户提供所有IP和浏览器-但是，如果用户在11月访问过该网站两次，则会计算两次，我只想计算一次。我想我可以用另一个难看的子选择来解决这个问题，但我正在寻找执行查询的最佳方式，因为表中有很多行。

据我所知，MySQL只能使用相关子查询或加入子查询来完成此操作

相关子查询：

SELECT
  count(browser), browser
FROM
  access
WHERE
      date = (SELECT MIN(date) FROM access AS lookup WHERE ip = access.ip)
  AND date > '2011-11-1'
  AND date < '2011-12-1' 
GROUP BY
  browser

SELECT
  count(access.browser), access.browser
FROM
  (SELECT ip, MIN(date) AS date FROM access GROUP BY ip) AS lookup
INNER JOIN
  access
    ON  access.ip   = lookup.ip
    AND access.date = lookup.date
WHERE
      lookup.date > '2011-11-1'
  AND lookup.date < '2011-12-1' 
GROUP BY
  access.browser

子查询：

SELECT
  count(browser), browser
FROM
  access
WHERE
      date = (SELECT MIN(date) FROM access AS lookup WHERE ip = access.ip)
  AND date > '2011-11-1'
  AND date < '2011-12-1' 
GROUP BY
  browser

SELECT
  count(access.browser), access.browser
FROM
  (SELECT ip, MIN(date) AS date FROM access GROUP BY ip) AS lookup
INNER JOIN
  access
    ON  access.ip   = lookup.ip
    AND access.date = lookup.date
WHERE
      lookup.date > '2011-11-1'
  AND lookup.date < '2011-12-1' 
GROUP BY
  access.browser

---

不管是哪种方式，请在ip上建立索引，date

我目前没有访问数据库的权限，但我假设您尝试了SELECT Differentip，但没有成功？Differentic和GROUP BY是互斥的。我非常确定我需要一个子查询，我只是担心我需要两个。。。谢谢需要注意的是，相关子查询的效率要高得多。