Mysql 如何在exec_datetime>；=现在（）-间隔n天？

我可以在单个时间范围内选择唯一ip地址的总数

SELECT COUNT(DISTINCT ip_address) as ip_addr, exec_datetime
FROM requests
WHERE exec_datetime >= NOW() - INTERVAL 1 DAY;

ip_addr exec_datetime
45      12/10/2012 5:21

如何在单个查询中返回以下子句的结果集

WHERE exec_datetime >= NOW() - INTERVAL 1 DAY;
WHERE exec_datetime >= NOW() - INTERVAL 2 DAY;
...
WHERE exec_datetime >= NOW() - INTERVAL 14 DAY;

…所以结果集是这样的

ip_addr exec_datetime
45      11/26/2012 5:21
85      11/27/2012 5:21
130     11/28/2012 5:21
170     11/29/2012 5:21
...     ...

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我会用这样的方式：

SELECT
  COUNT(DISTINCT requests.ip_address) ip_addr,
  days.day
FROM
  (SELECT now()-INTERVAL 1 DAY as day UNION
   SELECT now()-INTERVAL 2 DAY UNION
   ...
   SELECT now()-INTERVAL 14 DAY) days
  INNER JOIN requests
  on requests.exec_datetime >= days.day
GROUP BY
  days.day