Mysql，SUM 列和 GROUP BY HOUR

情况（简化）：

tableA

id |   date               | val
------------------------------
0    2018-02-19 00:01:00  | 10
1    2018-02-19 00:02:00  | 10
2    2018-02-19 00:03:00  | 10
..   2018-02-19 23:59:00  | 10

我需要执行一个查询，每小时返回列 val 的总和。

这是查询

SELECT `AllHours`.`hour` , COALESCE(SUM(`A`.`val`),0) AS `A`.`total`
FROM `tableA` AS `A`

RIGHT JOIN (
    SELECT  0 AS `hour`
    UNION ALL SELECT  1 UNION ALL SELECT  2 UNION ALL SELECT  3
         UNION ALL SELECT  4 UNION ALL SELECT  5 UNION ALL SELECT  6
         UNION ALL SELECT  7 UNION ALL SELECT  8 UNION ALL SELECT  9
         UNION ALL SELECT 10 UNION ALL SELECT 11 UNION ALL SELECT 12
         UNION ALL SELECT 13 UNION ALL SELECT 14 UNION ALL SELECT 15
         UNION ALL SELECT 16 UNION ALL SELECT 17 UNION ALL SELECT 18
         UNION ALL SELECT 19 UNION ALL SELECT 20 UNION ALL SELECT 21
         UNION ALL SELECT 22 UNION ALL SELECT 23
  )      AS `AllHours` ON HOUR(`A`.`date`) = `AllHours`.`hour`


WHERE `A`.`date` BETWEEN '2018-02-19 00:00:00' AND '2018-02-19 23:59:59' OR `A`.`date` IS NULL

GROUP BY `AllHours`.`hour`
ORDER BY `AllHours`.`hour`

Result

查询有效，但缺少 11 点。

重要的提示即使没有数据，我也需要一小时。否则我不会添加 RIGHT JOIN，并且按小时（日期）分组就足够了。

考虑使用数字表 - 请参阅下面的链接。这将为您提供目前所需的输出：

测试数据：

CREATE TABLE T   (`id` int, `dt` datetime, `val` int);        
INSERT INTO T    (`id`, `dt`, `val`) 
VALUES
    (0, '2018-02-19 00:01:00', 10),
    (1, '2018-02-19 00:02:00', 10),
    (2, '2018-02-19 00:03:00', 10),
    (4, '2018-02-19 01:01:00', 10),
    (5, '2018-02-19 01:02:00', 10),
    (6, '2018-02-19 02:03:00', 10)
;

Sql:

select 
  lpad(cast(HH as char(2)),2,'0') as hour,  
  sum(val) as sumVal from
(
    select 
      EXTRACT(HOUR from dt) AS HH,
      val
    from T 
    WHERE dt >= '2018-02-19 0:0:0' and dt < '2018-02-20 0:0:0'

    UNION ALL SELECT  0,0
    UNION ALL SELECT  1,0 UNION ALL SELECT  2,0  UNION ALL SELECT  3,0
    UNION ALL SELECT  4,0 UNION ALL SELECT  5,0  UNION ALL SELECT  6,0
    UNION ALL SELECT  7,0 UNION ALL SELECT  8,0 UNION ALL SELECT  9,0
    UNION ALL SELECT 10,0 UNION ALL SELECT 11,0 UNION ALL SELECT 12,0
    UNION ALL SELECT 13,0 UNION ALL SELECT 14,0 UNION ALL SELECT 15,0
    UNION ALL SELECT 16,0 UNION ALL SELECT 17,0 UNION ALL SELECT 18,0
    UNION ALL SELECT 19,0 UNION ALL SELECT 20,0 UNION ALL SELECT 21,0
    UNION ALL SELECT 22,0 UNION ALL SELECT 23,0
) as m
group by lpad(cast(HH as char(2)),2,'0')

为您提供以下输出：

hour    sumVal
00  30
01  20
02  10
03  0
04  0
05  0
06  0
07  0
08  0
09  0
10  0
11  0
12  0
13  0
14  0
15  0
16  0
17  0
18  0
19  0
20  0
21  0
22  0
23  0

如果您更频繁地需要此操作，请创建一个数字表并使用已有的联接语法。如果没有数字表，您也可以在不加入的情况下联合所有内容。

SO-阅读：

• MYSQL：序号表 https://stackoverflow.com/questions/14298154/mysql-sequential-number-table
• 在mysql中创建一个“数字表” https://stackoverflow.com/questions/9751318/creating-a-numbers-table-in-mysql

使用数字表，以上所有大联合可以重写为

UNION ALL SELECT  num, 0 from numbers where num between 0 and 23

或者您可以对其使用连接和合并语法。