A simple way to sum a result from UNION in MySQL - sql

Question

I have a union of three tables (t1, t2, t3).
Each rerun exactly the same number of records, first column is id, second amount:
1 10
2 20
3 20
1 30
2 30
3 10
1 20
2 40
3 50
Is there a simple way in SQL to sum it up, i.e. to only get:
1 60
2 80
3 80

Answer 1

select id, sum(amount) from (
select id,amount from table_1 union all
select id,amount from table_2 union all
select id,amount from table_3
) x group by id

Answer 2

SELECT id, SUM(amount) FROM
(
SELECT id, SUM(amount) AS `amount` FROM t1 GROUP BY id
UNION ALL
SELECT id, SUM(amount) AS `amount` FROM t2 GROUP BY id
) `x`
GROUP BY `id`
I groupped each table and unioned because i think it might be faster, but you should try both solutions.

Answer 3

Subquery:
SELECT id, SUM(amount)
FROM ( SELECT * FROM t1
UNION ALL SELECT * FROM t2
UNION ALL SELECT * FROM t3
)
GROUP BY id

Answer 4

Not sure if MySQL uses common table expression but I would do this in postgres:
WITH total AS(
SELECT id,amount AS amount FROM table_1 UNION ALL
SELECT id,amount AS amount FROM table_2 UNION ALL
SELECT id,amount AS amount FROM table_3
)
SELECT id, sum(amount)
FROM total
I think that should do the trick as well.

Answer 5

As it's not very clear from previous answers, remember to give aliases (on MySQL/MariaDb) or you'll get error:
Every derived table must have its own alias
select id, sum(amount) from (
select id,amount from table_1 union all
select id,amount from table_2 union all
select id,amount from table_3
) AS 'aliasWhichIsNeeded'
group by id

Answer 6

Yes!!! Its okay! Thanks!!!!
My code finishing:
SELECT SUM(total)
FROM (
(SELECT 1 as id, SUM(e.valor) AS total FROM entrada AS e)
UNION
(SELECT 1 as id, SUM(d.valor) AS total FROM despesa AS d)
UNION
(SELECT 1 as id, SUM(r.valor) AS total FROM recibo AS r WHERE r.status = 'Pago')
) x group by id

Answer 7

SELECT BANKEMPNAME, workStation, SUM (CALCULATEDAMOUNT) FROM(
SELECT BANKEMPNAME, workStation, SUM(CALCULATEDAMOUNT) AS CALCULATEDAMOUNT,SALARYMONTH
FROM dbo.vw_salaryStatement
WHERE (ITEMCODE LIKE 'A%')
GROUP BY BANKEMPNAME,workStation, SALARYMONTH
union all
SELECT BANKEMPNAME, workStation, SUM(CALCULATEDAMOUNT) AS CALCULATEDAMOUNT,SALARYMONTH
FROM dbo.vw_salaryStatement
WHERE (ITEMCODE NOT LIKE 'A%')
GROUP BY BANKEMPNAME, workStation, SALARYMONTH) as t1
WHERE SALARYMONTH BETWEEN '20220101' AND '20220131'
group by BANKEMPNAME, workStation
order by BANKEMPNAME asc
IN MSSQL You can write this way, But Doing UNION ALL THE Column should be the same for both ways.
I have given this example So that you can understand the process...