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：

利用SUM(IF()) 生成列 + WITH ROLLUP 生成汇总行,并利用 IFNULL将汇总行标题显示为 Total_num

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：