标签：test over flow add 修改 value ext 1.2 har
如何把mysql的列修改成行显示数据简单实现
创建测试表：
1: DROP TABLE IF EXISTS `test`;
2: CREATE TABLE `test` (
3: `year` int(11) DEFAULT NULL,
4: `month` int(11) DEFAULT NULL,
5: `amount` double DEFAULT NULL
6: ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
插入数据：
1: INSERT INTO `test` VALUES (‘1991‘, ‘1‘, ‘1.1‘);
2: INSERT INTO `test` VALUES (‘1991‘, ‘2‘, ‘1.2‘);
3: INSERT INTO `test` VALUES (‘1991‘, ‘3‘, ‘1.3‘);
4: INSERT INTO `test` VALUES (‘1991‘, ‘4‘, ‘1.4‘);
5: INSERT INTO `test` VALUES (‘1992‘, ‘1‘, ‘2.1‘);
6: INSERT INTO `test` VALUES (‘1992‘, ‘2‘, ‘2.2‘);
7: INSERT INTO `test` VALUES (‘1992‘, ‘3‘, ‘2.3‘);
8: INSERT INTO `test` VALUES (‘1992‘, ‘4‘, ‘2.3‘);
看到题目要求，仔细想想可以：
实现
SQL代码块如下：
1: select year,
2: sum(if(month=1,amount,0)) as "M1",
3: sum(if(month=2,amount,0)) as "M2",
4: sum(if(month=3,amount,0)) as "M3",
5: sum(if(month=4,amount,0)) as "M4"
6: from test
7: GROUP by year;
效果如下：
标签：test over flow add 修改 value ext 1.2 har
原文地址：http://www.cnblogs.com/HRuinger/p/5989839.html
