php - 如何使用 MySQL 在单个查询中运行两个不同的查询？

Question

我有一个包含这些列的发票表。

id total date         country
1   50   2016-01-25   USA
2   40   2016-01-24   UK
3   30   2016-01-22   France
4   40   2016-01-26   UK
5   50   2016-01-18   USA
6   60   2016-02-20   USA
7   70   2016-02-21   USA
8   55   2016-02-18   UK
9   75   2016-02-19   France

我想按月分组获取美国总金额、非美国总金额，我正在使用这些查询我只得到美国总金额

SELECT MONTH(date),YEAR(date),SUM(total) as usa_amount 
FROM Invoice 
WHERE YEAR(date) = '2016' 
  AND country='USA' 
GROUP BY MONTH(date)

我得到了这个结果

MONTH(date)  YEAR(date)   usa_amount
01            2016         100
02            2016         130

我想使用 mysql 联合或其他方式得到这个结果？

MONTH(date)  YEAR(date)   usa_amount  non_usa_amount
01            2016         100        110
02            2016         130        130

Answer 1

在sum()中使用case

SELECT MONTH(date),
       SUM(case when country =  'USA' then total else 0 end) as usa_amount,
       SUM(case when country <> 'USA' then total else 0 end) as non_usa_amount 
FROM Invoice 
WHERE YEAR(date) = 2016
GROUP BY MONTH(date)