我有一个名为STUDENTS的APACHE DERBY数据库表，其中包含以下行：
_____________________________
| NAME |COUNTER| MONTH |
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| bill | 10 | January |
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| bill | 12 | February|
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| bill | 11 | March |
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| sam | 14 | January |
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| sam | 9 | February|
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| sam | 22 | March |
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| hal | 21 | January |
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| hal | 18 | February|
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| hal | 19 | March |
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我试图找到语法来获得以下输出...
_________________________________
| NAME | JAN | FEB | MAR |
---------------------------------
| bill | 10 | 12 | 11 |
---------------------------------
| sam | 14 | 9 | 22 |
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| hal | 21 | 18 | 19 |
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我尝试了以下方法：
select distinct(name),
(SELECT COUNTER FROM STUDENTS WHERE NAME = 'bill' AND month = 'january') as jan,
(SELECT COUNTER FROM STUDENTS WHERE NAME = 'bill' AND month = 'february') as feb,
(SELECT COUNTER FROM STUDENTS WHERE NAME = 'bill' AND month = 'march') as mar
FROM STUDENT where name = 'bill'
......它可以作为一个学生的概念证明。但是，它是罗嗦的，它只适用于一个学生，并且它不会扩展我将添加到数据库的未来几个月的任何数据。意思是，我希望能够为每个NAME获取最后3个COUNTER值，而不管数据库中有多少个数据存在退出。
我看过多个s.o.与嵌套查询相关的问题，但没有一个有帮助。
建议？
任何帮助表示赞赏！
您可以使用条件聚合
SELECT name,
Max(CASE WHEN month = 'January' THEN counter end) AS jan,
Max(CASE WHEN month = 'February' THEN counter end) AS feb,
Max(CASE WHEN month = 'March' THEN counter end) AS mar
FROM student
GROUP BY name