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如何把mysql的列修改成行显示数据简单实现

2018-06-17 19:51:18来源：未知阅读 ()

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;