Question

我有以下树表

表士兵

ID   |   NAME 
---------------
22   |   Franck 
23   |   Paul 
24   |   Bill

表soldier_status_history

soldier_id   |            date_record       |     soldier_status 
-----------------------------------------------------------------          
22           |        2012-12-07 18:09:58   |          37 
22           |        2012-12-08 18:10:11   |          38 
22           |        2012-12-10 18:20:25   |          41 
23           |        2011-08-17 23:59:10   |          37 
23           |        2011-08-19 23:59:11   |          38 
23           |        2011-08-22 00:00:00   |          41  
23           |        2011-08-25 12:00:22   |          38   
24           |        2011-08-24 19:18:43   |          37  
24           |        2011-08-29 19:18:44   |          38

表soldier_values

id   |   key 
----------------
37   |   onduty 
38   |   available 
40   |   vacation 
41   |   ill

是否有可能成为一个将加入他们的选择，并且只返回来自表士兵_status_history的记录，对于特定士兵的最后日期_记录，soldier_status不是“假期”或“生病”

我的意思是这个名叫“保罗”的人我们有树记录，但最后一个记录他生病了，因为这个人不应该被显示，直到它的状态没有改变。

23      |        2011-08-17 23:59:10    |   37 
23      |        2011-08-19 23:59:11    |   38 
23      |        2011-08-22 00:00:00    |   41

Answer 1

select * from 
soldier s
left join 
(select 
     soldier_id, 
     max(date_record) maxDate_record
   from soldier_status_history 
   group by soldier_id
) s2 
    on (s.id=s2.soldier_id)
left join soldier_status_history s3 
    on (s2.soldier_id=s3.soldier_id) and (s2.maxDate_record=s3.date_record)

where s3.soldier_status not in (40,41)

Answer 2

试试这个：

SELECT
  h.*
FROM Soldier s 
INNER JOIN soldier_status_history h ON s.ID = h.soldier_id
INNER JOIN
(
  SELECT Soldier_id, MAX(date_record) latestDate
  FROM soldier_status_history 
  GROUP BY soldier_id
) l  ON h.soldier_id = s.ID
    AND DATE(l.latestDate) = DATE(h.date_record);

SQL Fiddle Demo

这会给你：

| SOLDIER_ID |                     DATE_RECORD | SOLDIER_STATUS |
-----------------------------------------------------------------
|         22 | December, 10 2012 18:20:25+0000 |             41 |
|         23 |   August, 25 2011 12:00:22+0000 |             38 |
|         24 |   August, 29 2011 19:18:44+0000 |             38 |

加入树表并根据日期层次结构获取最后一个状态

2 个答案:

SQL Fiddle Demo