MySQL 分组依据和计数...我可以进行嵌套分组吗？

Question

我有一个名为 activity 的表，它使用以下列:

LoginDate, LoginID, Department, IsMGR

我尝试了这个查询:

  SELECT COUNT(*), 
         DATE_FORMAT( LoginDate, '%m%d%Y' ) AS LogDate, 
         LoginID, Department
    FROM `activity` 
   WHERE IsMGR = '1' 
     AND LoginDate > '2011-01-01 00:00:00' 
GROUP BY LoginID, LogDate 
ORDER BY LoginID,LogDate DESC

我最终得到的是:

3   02172011    sdavis  accounting
1   02162011    sdavis  accounting
2   02132011    sdavis  accounting
1   02102011    sdavis  accounting
5   02092011    sdavis  accounting
4   02082011    sdavis  accounting
1   03182011    dmorris     marketing
1   03092011    dmorris     marketing
6   04142011    cchan   technology
1   03282011    cchan   technology
2   03262011    cchan   technology
2   03112011    cchan   technology
1   03102011    cchan   technology

这给出了他们每天登录的次数。我想要的是每天只进行一次计数，并将每个人的所有天数分组并计数他们登录的天数以及最后一天。使用上面的数据示例，我想要的输出应该是

6 02172011 sdavis accounting
2 03182011 dmorris marketing
5 04142011 cchan technology

所以我想要的是通过第二组标准对上述分组结果进行分组......？

Answer 1

试试这个:

SELECT COUNT(distinct LoginDate) AS NumLogins,
       DATE_FORMAT( MAX(LoginDate), '%m%d%Y' ) AS LastLogDate, 
       LoginID, Department
FROM activity 
WHERE IsMGR='1' AND LoginDate > '2011-01-01 00:00:00' 
GROUP BY LoginID, Department
ORDER BY LoginID, Department DESC