爲時間序列數據創建小時組MySQL

Question

我有一個MySQL數據庫，每15分鐘記錄一次數據。爲了簡單起見，讓我們假設有2個字段：

DATETIME Created 
Double Value 

我要提請這就需要用於每個小時的開口，最小值，最大值，和關閉值一小時的圖表。爲此，我需要將我的MySQL查詢結果返回給我的PHP來創建一個JSON。我想在MySQL查詢中這樣做，以便響應被緩存。

這是問題的一個例子，給出9個數據點，試圖讓2小時組：

Creation   Value 
2014-03-25 12:15:00 413.17011 
2014-03-25 12:00:00 414 
2014-03-25 11:45:00 415 
2014-03-25 11:30:00 415 
2014-03-25 11:15:00 415.5 
2014-03-25 11:00:00 415.5 
2014-03-25 10:45:00 416 
2014-03-25 10:30:00 416 
2014-03-25 10:15:00 415.99 

我需要：

Hour 1 (11:15:00 to 12:15:00) 
Open: 415.5 
Close: 413.17011 
High: 415.5 
Low: 413.17011 

Hour 2 (10:15:00 to 11:15:00) 
Open: 415.99 
Close: 415.5 
High: 416 
Low: 415.5 

當然了整整24個小時本會需要重複，這只是一個例子。 任何幫助真的很感激！

下面是例子（使用MySQL版本2.6.4-PL3）當前的MySQL轉儲：

-- 
-- Table structure for table `exampleTable` 
-- 

CREATE TABLE `exampleTable` (
    `created` datetime NOT NULL, 
    `value` double NOT NULL 
) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci; 

-- 
-- Dumping data for table `exampleTable` 
-- 

INSERT INTO `exampleTable` VALUES ('2014-03-25 12:15:00', 413.17011); 
INSERT INTO `exampleTable` VALUES ('2014-03-25 12:00:00', 414); 
INSERT INTO `exampleTable` VALUES ('2014-03-25 11:45:00', 415); 
INSERT INTO `exampleTable` VALUES ('2014-03-25 11:30:00', 415); 
INSERT INTO `exampleTable` VALUES ('2014-03-25 11:15:00', 415.5); 
INSERT INTO `exampleTable` VALUES ('2014-03-25 11:00:00', 415.5); 
INSERT INTO `exampleTable` VALUES ('2014-03-25 10:45:00', 416); 
INSERT INTO `exampleTable` VALUES ('2014-03-25 10:30:00', 416); 
INSERT INTO `exampleTable` VALUES ('2014-03-25 10:15:00', 415.99); 

Answer 1

得到它的工作

你可以嘗試

SELECT 
DATE(created) AS day, 
HOUR(created) AS hour, 
(
    SELECT Value FROM `table` AS b 
    WHERE DATE(a.created) = DATE(b.created) 
    AND HOUR(a.created) = HOUR(b.created) 
    ORDER BY created ASC LIMIT 1 
) AS Open, 
(
    SELECT Value FROM `table` AS b 
    WHERE DATE(a.created) = DATE(b.created) 
    AND HOUR(a.created) = HOUR(b.created) 
    ORDER BY created DESC LIMIT 1 
) AS Close, 
MIN(value) AS Low, 
MAX(value) AS High 
FROM `table` AS a 
GROUP BY DATE(created), HOUR(created) 

這將所有行按DATE + HOUR分組，然後分別計算MAX分別爲Low或High。要找到Open和Close的第一行和最後一行，最簡單的SQL語法是子查詢。它選擇與當前行相關的所有行，並對它們進行升序或降序排序。然後選擇第一行。

請認爲這個小組只有小時。取而代之的

Hour 1 (11:15:00 to 12:15:00) 
Hour 2 (10:15:00 to 11:15:00) 

這個羣體喜歡

Hour 1 (11:00:00 to 11:59:00) 
Hour 2 (10:00:00 to 10:59:00) 

如果你想保持15分鐘偏差，您可以從您所創建的時間戳（created - INTERVAL 15 MINUTE）在created所有出現在SQL查詢中減去這個上面。

我爲您創建了a working sqlfiddle。

性能

正如提示：如果可以的話，你可能想的日期和時間分爲兩列（類型date和time）。這種方式你不需要每次都在created上投DATE()，而是可以使用新的日期列。然後，您可以將組合索引添加到這些新列中，從而加快查詢速度。以this sqlfiddle爲例。

Answer 2

爲了讓您的分組的權利，你可以使用

FLOOR((UNIX_TIMESTAMP(myTable.dateCreated) - 900)/3600) 

，其中3600在1小時，設定的時間間隔 - 900套00:15

偏移既然你需要的MIN（）和MAX分別代表你的四個值，你需要將主表加入自己，但是按最小或最大（基於列）進行分組。

最後，你有每個子查詢（連接表）計算上面的分組小時，所以你可以用它來加入它們。這是我凸輪了（略有不同的列名和

SELECT openDate,Open,Close,High,Low 
FROM (SELECT FLOOR((UNIX_TIMESTAMP(myTable.dateCreated) - 900)/3600) 
       AS 
         theHour, 
         myTable.value AS Open,myTable.dateCreated openDate 
     FROM myTable 
       JOIN (SELECT value,MIN(dateCreated) AS dateCreated 
        FROM myTable 
        GROUP BY FLOOR((UNIX_TIMESTAMP(dateCreated) - 900) 
            /3600) 
        ) AS 
            aggTable 
       ON aggTable.dateCreated = myTable.dateCreated) AS 
     openTable 
     LEFT JOIN (SELECT FLOOR((UNIX_TIMESTAMP(myTable.dateCreated) - 900 
           )/
           3600) AS 
     theHour 
     , 
     myTable.value AS Close,myTable.dateCreated closeDate 
     FROM myTable 
     JOIN (SELECT value,MAX(dateCreated) AS dateCreated 
     FROM myTable 
     GROUP BY FLOOR((UNIX_TIMESTAMP(dateCreated) - 900)/3600) 
     ) AS 
     aggTable 
     ON aggTable.dateCreated = myTable.dateCreated) AS closeTable 
       ON openTable.theHour = closeTable.theHour 
     LEFT JOIN (SELECT 
                 FLOOR(( 
       UNIX_TIMESTAMP(myTable.dateCreated) - 900)/3600) AS 
        theHour, 
                  MAX( 
                    value) 
       AS High 
        FROM myTable 
        GROUP BY theHour) AS highTable 
       ON closeTable.theHour = highTable.theHour 
     LEFT JOIN (SELECT 
                 FLOOR(( 
       UNIX_TIMESTAMP(myTable.dateCreated) - 900)/3600) AS 
        theHour, 
                  MIN( 
                    value) 
       AS Low 
        FROM myTable 
        GROUP BY theHour) AS lowTable 
       ON highTable.theHour = lowTable.theHour