mysql - 将两个表中的值按月求和

Question

如何将两个表中的值按月求和？

我有两个表:

1)costs_1

-id
-total
-updated_at(timestamp)

2)costs_2

-id
-total_1
-updated_at_1(timestamp)

结果表需要有下一列:

-total
-total_1
-month

例如，如果我有一个表，我会执行下一个查询:

SELECT SUM(total), MONTH(updated_at), YEAR(updated_at) FROM product_sale GROUP BY MONTH(updated_at), YEAR(updated_at) ORDER by MONTH(updated_at)

Answer 1

我相信你想要这样的东西。

SELECT t1.y year,
       t1.m month,
       t1.total,
       t2.total
FROM
(
    SELECT YEAR(updated_at) y, 
           MONTH(updated_at) m, 
           SUM(total) total
    FROM costs_1
    GROUP BY YEAR(updated_at), MONTH(updated_at) 
) t1
JOIN
(
    SELECT YEAR(updated_at_1) y, 
           MONTH(updated_at_1) m, 
           SUM(total_1) total
    FROM costs_2
    GROUP BY YEAR(updated_at_1), MONTH(updated_at_1) 
) t2 ON t1.y = t2.y and t1.m = t2.m

但是，在此解决方案中，如果 costs_1 或 costs_2 没有该月份的任何记录，您将错过该月份。如果你想要 FULL JOIN，你必须使用两个 OUTER JOINS 在 mysql 中模拟它，如下所示:

SELECT t1.y year,
       t1.m month,
       COALESCE(t1.total, 0),
       COALESCE(t2.total, 0)
FROM
(
    SELECT YEAR(updated_at) y, 
           MONTH(updated_at) m, 
           SUM(total) total
    FROM costs_1
    GROUP BY YEAR(updated_at), MONTH(updated_at) 
) t1
LEFT JOIN
(
    SELECT YEAR(updated_at_1) y, 
           MONTH(updated_at_1) m, 
           SUM(total_1) total
    FROM costs_2
    GROUP BY YEAR(updated_at_1), MONTH(updated_at_1) 
) t2 ON t1.y = t2.y and t1.m = t2.m

   UNION

SELECT t2.y year,
       t2.m month,
       COALESCE(t1.total, 0),
       COALESCE(t2.total, 0)
FROM
(
    SELECT YEAR(updated_at) y, 
           MONTH(updated_at) m, 
           SUM(total) total
    FROM costs_1
    GROUP BY YEAR(updated_at), MONTH(updated_at) 
) t1
RIGHT JOIN
(
    SELECT YEAR(updated_at_1) y, 
           MONTH(updated_at_1) m, 
           SUM(total_1) total
    FROM costs_2
    GROUP BY YEAR(updated_at_1), MONTH(updated_at_1) 
) t2 ON t1.y = t2.y and t1.m = t2.m