有一張表，資料如下
請寫出結果為以下的SQL語句。
在mysql中建立表
CREATE TABLE `aa` (
`id` int(10) NOT NULL AUTO_INCREMENT COMMENT '書籍編號',
`year` varchar(4) NOT NULL DEFAULT '' COMMENT '年',
`month` varchar(2) NOT NULL DEFAULT '0' COMMENT '月份',
`mount` double DEFAULT NULL COMMENT '數量',
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;
插入資料：
insert into aa(year,month,mount) values(2011,1,1.1),(2011,2,1.2),(2011,3,1.3),(2011,4,1.4);
insert into aa(year,month,mount) values(2012,1,2.1),(2012,2,2.2),(2012,3,2.3),(2012,4,2.4);
insert into aa(year,month,mount) values(2013,1,3.1),(2013,2,3.2),(2013,3,3.3),(2013,4,3.4);
insert into aa(year,month,mount) values(2014,1,4.1),(2014,2,4.2),(2014,3,4.3),(2014,4,4.4);
查詢語句為：
select t2.year,(select t1.mount from aa t1 where t1.year = t2.year and t1.month = 1) m1,
(select t1.mount from aa t1 where t1.year = t2.year and t1.month = 2) m2,
(select t1.mount from aa t1 where t1.year = t2.year and t1.month = 3) m3,
(select t1.mount from aa t1 where t1.year = t2.year and t1.month = 4) m4 from
aa t2 group by t2.year order by t2.year;
完畢。
備註：簡單的實現了一下，若您有更好的，若方便可以共享一下；若有什麼錯誤，請指出，謝謝！