在 MySQL 中对 UNION 结果求和的简单方法

Question

我有三个表（t1、t2、t3）的并集。
每次重新运行完全相同数量的记录，第一列是id，第二列amount：

1  10
2  20
3  20

1  30
2  30
3  10

1  20
2  40
3  50

SQL中有没有一种简单的方法来总结它，即只得到：

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`

我对每个表进行分组并联合，因为我认为它可能会更快，但您应该尝试这两种解决方案。

Answer 3

子查询：

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

Answer 4

不确定 MySQL 是否使用公用表表达式，但我会在 postgres 中执行此操作：

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

我认为这也应该可以解决问题。

Answer 5

由于之前的答案不是很清楚，请记住提供别名（在 MySQL/MariaDb 上），否则您会收到错误：

每个派生表必须有自己的别名

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

是的！！！没关系！谢谢！！！！
我的代码整理：

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

在 MSSQL 中，您可以这样编写，但是执行 UNION ALL 列对于两种方式应该是相同的。

我给出了这个例子，以便您可以理解这个过程......