避免重複子查詢

我有一個表消息包含一列message_internaldate。現在我想在幾個月內的特定時間段內（一天中的每個小時）對這些消息進行計數。我可以設法通過大量的子查詢來獲得每小時的消息總數（24），但我希望有一個更聰明的方式來做到這一點。除了時間段發生變化外，子查詢是相似的。有什麼建議麼？避免重複子查詢

例如前兩個小時

SELECT T1, T2 FROM 
(
SELECT sum(T1c) as T1 FROM 
    (
    SELECT strftime('%H:%M',message_internaldate) AS T1s ,count(*) as T1c FROM messages WHERE 
    message_internaldate BETWEEN '2005-01-01 00:00:00' AND '2012-12-31 00:00:00' 
    AND strftime('%H:%M',message_internaldate) BETWEEN '01:00'AND '01:59' 
    GROUP BY strftime('%H:%M',message_internaldate) 
    ) 
) 
, 
(
SELECT sum(T2c) as T2 FROM 
    (
    SELECT strftime('%H:%M',message_internaldate) AS T2s ,count(*) as T2c FROM messages WHERE 
    message_internaldate BETWEEN '2005-01-01 00:00:00' AND '2012-12-31 00:00:00' 
    AND strftime('%H:%M',message_internaldate) BETWEEN '02:00'AND '02:59' 
    GROUP BY strftime('%H:%M',message_internaldate) 
    ) 
) 
...

來源

2013-03-18 Durin

你的問題是，你想有個別小時爲列。

爲了讓他們爲行，嘗試這樣的查詢：

SELECT strftime('%H', message_internaldate) AS hour, 
     strftime('%H:%M', message_internaldate) AS Ts, 
     COUNT(*) AS Tc 
FROM messages 
WHERE message_internaldate BETWEEN '2005-01-01 00:00:00' AND '2012-12-31 23:59:59' 
GROUP BY 1, 2

來源

2013-03-18 10:59:35

謝謝！我說：選擇時，總和（TC）爲SumOfMails FROM （您的查詢）GROUP BY小時這不正是我原本想做的事！ – Durin 2013-03-18 11:31:25

避免重複子查詢

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