Sum childrens in two tables of a table - mysql

Question

I Have 3 tables:
a (id,date,ckey) b(id,a.ckey,hht,hha) c(id,a.ckey,date_ini,date_fin)
where B keeps all the activities to be done and their respective hours in 2 places (hht,hha), while c saves the activities carried out with its initial and final date (to determine the hours executed the dates are subtracted).
Now I need to know, for each record in A how many hours you have assigned (B) and how many hours you have completed (C)
actually i have this:
a:
+----------+----------+------------+
| id | date | ckey |
+----------+----------+------------+
| 1 |2018-01-20| 18 |
|----------|----------|------------|
b:
+----------+----------+--------+--------+
| id | a.ckey | hht | hht |
+----------+----------+--------+--------+
| 1 | 18 | 2 | 3 |
| 2 | 18 | 2 | 5 |
| 3 | 18 | 0 | 7 |
+----------+----------+--------+--------+
c:
+----------+----------+----------------------+----------------------+
| id | a.ckey | date_ini | date_fin |
+----------+----------+----------------------+----------------------+
| 1 | 18 | 2019-01-23 13:30:00 | 2019-01-23 14:00:00 |
| 1 | 18 | 2019-01-23 14:00:00 | 2019-01-23 14:30:00 |
+----------+----------+----------------------+----------------------+
I need this:
+----------+----------+----------------------+----------------------+
| id | a.ckey | hours | hours2 |
+----------+----------+----------------------+----------------------+
| 1 | 18 | 19 | 1 |
+----------+----------+----------------------+----------------------+
I get this:
+----------+----------+----------------------+----------------------+
| id | a.ckey | hours | hours2 |
+----------+----------+----------------------+----------------------+
| 1 | 18 | 38 | 37.5 |
+----------+----------+----------------------+----------------------+
This is my query:
SELECT
(b.hht+b.hha) AS hours,
(SUM(b.hht+b.hha) -
FORMAT(IFNULL((TIMESTAMPDIFF(MINUTE, c.date_ini, c.date_fin)/60),0),2)) AS hours2
FROM a
LEFT JOIN b ON a.key=b.akey
INNER JOIN c ON a.key=c.akey
GROUP a.ckey

Answer 1

Because you have multiple rows in tables b and c for each value of ckey you need to do the aggregation within a subquery, otherwise you get duplicated rows leading to incorrect sums.
SELECT a.id, a.key, b.hours, FORMAT(c.minutes/60, 2) AS hours2
FROM a
LEFT JOIN (SELECT akey, SUM(hht+hha) AS hours
FROM b
GROUP BY akey) b ON b.akey = a.key
LEFT JOIN (SELECT akey, SUM(TIMESTAMPDIFF(MINUTE, date_ini, date_fin)) AS minutes
FROM c
GROUP BY akey) c ON c.akey = a.key
ORDER BY a.id
Output:
id key hours hours2
1 18 19 1.00
Demo on SQLFiddle

Answer 2

You're doing an m-to-n-join, try UNION ALL instead:
select ckey, sum(hours) as hours, sum(hours) - sum(hours2) as hours2
from
(
SELECT ckey, (b.hht+b.hha) AS hours, NULL as hours2
FROM b
UNION ALL
SELECT ckey, NULL AS hours,
FORMAT(IFNULL((TIMESTAMPDIFF(MINUTE, c.date_ini, c.date_fin)/60),0),2)) as hours2
FROM c
) as dt
group by ckey
If you actually need columns from table a put this Select in a Derived Table and join to it.

Answer 3

please check this
SELECT
(SELECT SUM(hha + hht) from b where b.ckey = a.ckey) hours,
FORMAT((SELECT SUM(TIMESTAMPDIFF(MINUTE, c.date_ini, c.date_fin)/60) from c where c.ckey = a.ckey),2) as hours2
FROM A
Fiddle