MYSQL - Select total amount of 3 joined table - mysql

Question

I have 3 tables:
table a => id, name
table b => id, id_a, amount
table c => id, id_a, amount
How can I select table a and the total amount from table b, and table c?
I already have tried:
SELECT a.`name`, SUM(b.`amount`) AS Total
FROM a
LEFT JOIN b ON a.`id` = b.`id_a`
UNION
SELECT a.`name`, SUM(c.`amount`) AS Total
FROM a
RIGHT JOIN c ON a.`id` = c.`id_a`
GROUP BY a.`id`
But it shows multiple records from table a where there is id_a value in both table b and table c.
FYI: if table a is inserted, so table b or table c or both table b and table c will be inserted the detail. So there is no possible table a has no detail in table a or table b
here is the example data
table a:
id | name
1 | name 1
2 | name 2
table b:
id | id_a | amount
1 | 1 | 300
2 | 1 | 200
table c:
id | id_a | amount
1 | 1 | 200
2 | 1 | 100
3 | 2 | 300
4 | 2 | 100
Preferred Result:
name | amount
name 1 | 800
name 2 | 400
UPDATE THE ANSWER => Thanks to #Jens
SELECT d.NAME, SUM(d.Total) FROM (
SELECT a.id AS id , a.`name` AS NAME, SUM(b.`amount`) AS Total
FROM a
LEFT JOIN b ON a.`id` = b.`id_a`
GROUP BY a.`id`
UNION
SELECT a.`id` AS id, a.`name`, SUM(c.`amount`) AS Total
FROM a
RIGHT JOIN c ON a.`id` = c.`id_a`
GROUP BY a.`id`
) AS d
GROUP BY d.`id`
ANOTHER ANSWER FROM #Alex IS WORKING TOO AND SIMPLER
Thanks to both #Jens and #Alex. It's increase my knowledge

Answer 1

Try
select d.name, sum(d.total) from (
SELECT a.id as id , a.`name` as name, b.`amount` AS Total
FROM a
LEFT JOIN b ON a.`id` = b.`id_a`
UNION
SELECT a.id as id a.`name`, c.`amount` AS Total
FROM a
RIGHT JOIN c ON a.`id` = c.`id_a`
) as d
GROUP BY d.`id`
UPDATED:
SELECT d.NAME, SUM(d.Total) FROM (
SELECT a.id AS id , a.`name` AS NAME, SUM(b.`amount`) AS Total
FROM a
LEFT JOIN b ON a.`id` = b.`id_a`
GROUP BY a.`id`
UNION
SELECT a.`id` AS id, a.`name`, SUM(c.`amount`) AS Total
FROM a
RIGHT JOIN c ON a.`id` = c.`id_a`
GROUP BY a.`id`
) AS d
GROUP BY d.`id`

Answer 2

Have you tried this?
SELECT a.name, sum(b.amount), sum(c.amount)
FROM a
JOIN b on a.id = b.id_a
JOIN c on a.id = c.id_a
GROUP BY a.id
not sure about the relations, but you can replace JOIN with LEFT JOIN if that's your case.
UPDATE
This should be working:
SELECT a.name as "name", sum(d.amount) as "amount"
FROM a
JOIN (SELECT id_a, amount FROM b UNION ALL SELECT id_a, amount FROM c) as d
on d.id_a = a.id
group by a.name
This yields the following results:
name1 | 800
name2 | 400