MySql查询组按天和按时间

Question

我想创建一个SQL查询来解决我的问题。

我的表：

+----+---------------------+-------+ 
| id |   date  | value | 
+----+---------------------+-------+ 
| 1 | 2014-10-10 05:10:10 | 10 | 
+----+---------------------+-------+ 
| 2 | 2014-10-10 09:10:10 | 20 | 
+----+---------------------+-------+ 
| 3 | 2014-10-10 15:10:10 | 30 | 
+----+---------------------+-------+ 
| 4 | 2014-10-10 23:10:10 | 40 | 
+----+---------------------+-------+ 
| 5 | 2014-10-11 08:10:10 | 15 | 
+----+---------------------+-------+ 
| 6 | 2014-10-11 09:10:10 | 25 | 
+----+---------------------+-------+ 
| 7 | 2014-10-11 10:10:10 | 30 | 
+----+---------------------+-------+ 
| 8 | 2014-10-11 23:10:10 | 40 | 
+----+---------------------+-------+ 

我想天总结在组值，这天三个亚组类似“早晨”（06:00 - 12:00），“午”（ 12:00 - 18:00）和'晚上'（00:00 - 06:00和18:00 - 24:00）。
是这样的：

+------------+-------+---------+-----------+-------+ 
| date | value | morning | afternoon | night | 
+------------+-------+---------+-----------+-------+ 
| 2014-10-10 | 100 | 20 |  30 | 50 | 
+------------+-------+---------+-----------+-------+ 
| 2014-10-11 | 110 | 70 |  0  | 40 | 
+------------+-------+---------+-----------+-------+ 

Answer 1

你可以用一对夫妇的sum结束了case表达式：

SELECT DAY(`date`) AS `date` 
     SUM(CASE WHEN HOUR(`date`) BETWEEN 6 AND 12 THEN value ELSE 0 END) AS `morning`, 
     SUM(CASE WHEN HOUR(`date`) BETWEEN 12 AND 18 THEN value ELSE 0 END) AS `afternoon`, 
     SUM(CASE WHEN HOUR(`date`) < 6 OR HOUR(`date`) > 18 THEN value ELSE 0 END) AS `evening` 
FROM  my_table 
GROUP BY DAY(`date`) 

Answer 2

有多种方法去了解这一点，但我自己我会做通过首先提取CROSS APPLY中的伪信息，然后将该信息分组。

我相信这提供了重要的可读性好处，并允许您在其他子句中重新使用任何计算。例如，你已经集中了分组机制，这意味着你只需要在一个地方而不是在select和group by中进行更改。同样，您可以将“extraData.Morning = 1”添加到WHERE子句中，而不是重新编写早上的计算。

例如：

CREATE TABLE #TestData (ID INT, Data DATETIME, Value INT) 

INSERT INTO #TestData (ID, Data, Value) VALUES 
    (1 ,'2014-10-10 05:10:10' ,10) 
    ,(2 ,'2014-10-10 09:10:10' ,20) 
    ,(3 ,'2014-10-10 15:10:10' ,30) 
    ,(4 ,'2014-10-10 23:10:10' ,40) 
    ,(5 ,'2014-10-11 08:10:10' ,15) 
    ,(6 ,'2014-10-11 09:10:10' ,25) 
    ,(7 ,'2014-10-11 10:10:10' ,30) 
    ,(8 ,'2014-10-11 23:10:10' ,40) 

SELECT 
    extraData.DayComponent 
    ,SUM(td.Value) 
    ,SUM(CASE WHEN extraData.Morning = 1 THEN td.Value ELSE 0 END) AS Morning 
    ,SUM(CASE WHEN extraData.Afternoon = 1 THEN td.Value ELSE 0 END) AS Afternoon 
    ,SUM(CASE WHEN extraData.Night = 1 THEN td.Value ELSE 0 END) AS Night 
FROM #TestData td 
    CROSS APPLY (
     SELECT 
      DATEADD(dd, 0, DATEDIFF(dd, 0, td.Data))  AS DayComponent 
      ,CASE WHEN DATEPART(HOUR, td.Data) BETWEEN 6 AND 12 THEN 1 ELSE 0 END AS Morning 
      ,CASE WHEN DATEPART(HOUR, td.Data) BETWEEN 12 AND 18 THEN 1 ELSE 0 END AS Afternoon 
      ,CASE WHEN DATEPART(HOUR, td.Data) BETWEEN 0 AND 6 
       OR DATEPART(HOUR, td.Data) BETWEEN 18 AND 24 THEN 1 ELSE 0 END AS Night 
    ) extraData 
GROUP BY 
    extraData.DayComponent 

DROP TABLE #TestData