有關更新的Mysql問題

Question

UPDATE counter_reports 
SET `counter`=`counter`+1,`date`=? 
WHERE report_id IN(
        (SELECT report_id 
        FROM counter_reports 
        WHERE report_name="emails_sent" AND `year`=1 
        ORDER BY report_id DESC LIMIT 1), 
        (SELECT report_id 
        FROM counter_reports 
        WHERE report_name="emails_sent" AND `month`=1 
        ORDER BY report_id DESC LIMIT 1), 
        (SELECT report_id 
        FROM counter_reports 
        WHERE report_name="emails_sent" AND `week`=1 
        ORDER BY report_id DESC LIMIT 1), 
        (SELECT report_id 
        FROM counter_reports 
        WHERE report_name="emails_sent" AND `day`=1 
        ORDER BY report_id DESC LIMIT 1) 
       ) 

是否有任何替代這種SQL？我需要更新（增加1）最後的櫃檯報告日，周，月和年。

如果我手動添加，SQL工作正常，但對子查詢無法啓動。

謝謝。 :)

Answer 1

MySQL是有點跛，做到這一點，那將工作：

UPDATE counter_reports 
SET `counter`=`counter`+1,`date`=? 
WHERE report_id IN(
        (select report_id from (SELECT report_id 
        FROM counter_reports 
        WHERE report_name="emails_sent" AND `year`=1 
        ORDER BY report_id DESC LIMIT 1) as x), 
        (select report_id from (SELECT report_id 
        FROM counter_reports 
        WHERE report_name="emails_sent" AND `month`=1 
        ORDER BY report_id DESC LIMIT 1) as x), 
        (select report_id from (SELECT report_id 
        FROM counter_reports 
        WHERE report_name="emails_sent" AND `week`=1 
        ORDER BY report_id DESC LIMIT 1) as x), 
        (select report_id from (SELECT report_id 
        FROM counter_reports 
        WHERE report_name="emails_sent" AND `day`=1 
        ORDER BY report_id DESC LIMIT 1) as x) 
       ) 

也看看這裏的最後一個例子（MySQL的代碼，關係到你的問題）：http://mssql-to-postgresql.blogspot.com/2007/12/deleting-duplicates-in-postgresql-ms.html

Answer 2

什麼是不工作，什麼是錯誤？

以上的子查詢可能會有點改善

SELECT report_id 
FROM counter_reports 
WHERE report_name="emails_sent" AND `year`=1 
ORDER BY report_id DESC LIMIT 1 

相當於

SELECT max(report_id) 
FROM counter_reports 
WHERE report_name="emails_sent" AND `year`=1 

，並在情況下，有超過REPORT_NAME，同比指數和REPORT_ID它可能是快。

編輯：如果你遇到ERROR 1093 (HY000): You can't specify target table 'table_name' for update in FROM clause有一個workaround爲此。

一般來說，上面有點難看，我想它不會顯示變得漂亮的跡象。處理上述問題的方法之一，尤其是因爲這顯然是多步驟過程的一部分，所以將這四個ID存儲在某個轉換表中，以便它們可以被過程的不同部分重複使用生成報告。

或者跟蹤應用程序端的ID也是有效的（將它們作爲參數傳遞給更新它們的函數等）。