Mysql , SUM column and GROUP BY HOUR - mysql

Question

Situation (simplified):
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
I need to do a query that return for each hour the SUM of the column val.
This is the query
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
The query works, but hour 11 is missing.
Important note
I need all the hour, also if there aren't data. Otherwise i wouldn't have added the RIGHT JOIN and it would have been enough a GROUP BY HOUR(date).

Answer 1

Consider using a numbers table - see links below. This will give you the desired output for now:
Testdata:
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')
gets you an output of:
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
If you need this more often, create a numbers table and use the join syntax you already have. Without a numbers table you can as well union all without join.
SO-Readups:
MYSQL: Sequential Number Table
Creating a "Numbers Table" in mysql
With a numbers table the big union all above could be rewritten to
UNION ALL SELECT num, 0 from numbers where num between 0 and 23
or you could use a join on it and your coalesce syntax.

Answer 2

try it:
SELECT
`AllHours`.`tmp_hour`,
COALESCE(SUM(`val`),0) AS `total`
FROM
tableA
RIGHT JOIN (
SELECT 0 AS `tmp_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 DATE_FORMAT(dt, '%H') = `AllHours`.`tmp_hour`
WHERE `dt` BETWEEN '2018-02-19 00:00:00' AND '2018-02-19 23:59:59' OR `dt` IS NULL
GROUP BY `AllHours`.`tmp_hour`
ORDER BY `AllHours`.`tmp_hour`