如何以檢索最後更新的記錄在甲骨文

Question

嗨能否請你幫我對於這種情況，

表：Mail_Archives

Mail_ID  Archived_by   Archived_date 
    001  Sam    21/11/2011 
    002  Tina    10/10/2012 
    002  Tina    10/10/2012 
    004  Zark    10/10/2011 

如何形成這種輸出的查詢，我需要查詢結果包括計數在內的最近歸檔日期。例

Count  Archived_by  Archived_Date 

    2   Tina   10/10/2012 

Answer 1

嘗試：

select * from (
    select * from Mail_Archives order by Archived_date desc 
) where rownum=1 

更新：

select count(a.Mail_ID) top_one, b.archived_by, b.archived_date 
from Mail_Archives a, 
    (select * from (
      select * from Mail_Archives order by Archived_date desc 
     ) where rownum=1 
    ) b 
where a.archived_by = b.archived_by 
group by b.archived_by, b.archived_date 

你可以看到，它的工作原理here

Answer 2

這是一個MySQL查詢，我不知道有Oracle來測試它，但它可能會給你一個很好的嘗試。 注意：表名稱爲'測試'。 極限1將只需要最上面的一個（示出最大計數） 上或在表小寫屬性使得在查詢中沒有差別，另外，整數前00將被默認

SELECT COUNT(mail_ID) as top_one, archived_by, archived_date 
FROM test 
GROUP BY mail_id 
HAVING COUNT(*) = (
    SELECT COUNT(*) AS total 
    FROM test 
    GROUP BY mail_id 
    ORDER BY total DESC 
    LIMIT 1 
) 


top_one  archived_by  archived_date 
2   Tina    2012-10-10 

Answer 3

嘗試截斷：

select mail_id, archived_by, archived_date, cnt 
from (
select mail_id, archived_by, archived_date, count(*) cnt 
from Mail_Archives 
group by mail_id, archived_by, archived_date 
order by archived_date desc) 
where rownum = 1; 

或者（如果你喜歡的窗函數）

select mail_id, archived_by, archived_date, cnt from (
select mail_id, 
     archived_by, 
     archived_date, 
     row_number() over (order by archived_date desc) rn, 
     count(*) over (partition by mail_id, archived_by, archived_date) cnt 
from Mail_Archives) 
where rn = 1; 

Here is a sqlfiddle demo

---

UPDATE假設你想要的最大日期和次數，僅用於mail_id

select mail_id, archived_by, archived_date, cnt from (
select mail_id, 
     archived_by, 
     archived_date, 
     row_number() over (order by archived_date desc) rn, 
     count(*) over (partition by mail_id) cnt 
from Mail_Archives) 
where rn = 1; 

Here is a sqlfiddle demo