Mysql 选择给定年份的金额

我有一张表格，上面有国家、年份和每年的金额。我正在尝试编写一个查询，将给定年份的总金额相加，并将其作为列提供给我

例如，要获得如下输出：

Country   1991     1992     1993
France     25       12       38

我尝试过这样的查询，但没有成功：

SELECT 
     country as "Recipient", 
     SUM(usd_amount) AS "1991" WHEN project_year = 1991,
     SUM(usd_amount) AS "1992" WHEN project_year = 1992,
     SUM(usd_amount) AS "1993" WHEN project_year = 1993

FROM tb1

GROUP BY project_year, country
order by country, project_year

有什么建议吗？ 谢谢 克里斯

试试看：

SELECT 
     country as "Recipient", 
     SUM(if(project_year = 1991, usd_amount, 0)) AS "1991",
     SUM(if(project_year = 1992, usd_amount, 0)) AS "1992",
     SUM(if(project_year = 1993, usd_amount, 0)) AS "1993",
FROM tb1
GROUP BY country
ORDER BY country

PS：按项目年订购是没有意义的，因为您已经在进行聚合了。

请尝试以下方法

SELECT 
     country as "Recipient", 
     SUM(case WHEN project_year = 1991 then usd_amount else 0 end) AS "1991" ,
     SUM(case WHEN project_year = 1992 then usd_amount else 0 end) AS "1992" ,
     SUM(case WHEN project_year = 1993 then usd_amount else 0 end) AS "1993" 

FROM tb1

GROUP BY country, project_year
order by country, project_year

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共享表中存储的数据示例。