问题 行列互换

场景1 行转换列

1、表结构和数据

/*Navicat Premium Data TransferSource Server         : 本地Source Server Type    : MySQLSource Server Version : 80027Source Host           : localhost:3306Source Schema         : schoolTarget Server Type    : MySQLTarget Server Version : 80027File Encoding         : 65001Date: 13/06/2024 14:50:51
*/SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;-- ----------------------------
-- Table structure for score
-- ----------------------------
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score`  (`stu_no` varchar(128) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '学号',`course_no` varchar(128) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL COMMENT '课程号',`score_prize` decimal(4, 1) NULL DEFAULT NULL COMMENT '成绩',PRIMARY KEY (`stu_no`, `course_no`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Dynamic;-- ----------------------------
-- Records of score
-- ----------------------------
INSERT INTO `score` VALUES ('0001', '0001', 40.0);
INSERT INTO `score` VALUES ('0001', '0002', 50.0);
INSERT INTO `score` VALUES ('0001', '0003', 48.0);
INSERT INTO `score` VALUES ('0002', '0001', 40.0);
INSERT INTO `score` VALUES ('0002', '0002', 30.0);
INSERT INTO `score` VALUES ('0002', '0003', 99.0);
INSERT INTO `score` VALUES ('0003', '0001', 70.0);
INSERT INTO `score` VALUES ('0003', '0002', 77.0);
INSERT INTO `score` VALUES ('0003', '0003', 60.0);SET FOREIGN_KEY_CHECKS = 1;

2、效果图说明，第一列用户信息stu_no,第二列课程号course_no,第三列课程成绩

stu_no	语文	数学	英语
0001	40.0	50.0	48.0
0002	40.0	30.0	99.0
0003	70.0	77.0	60.0

3、实现SQL

select stu_no,sum(IF(course_no = '0001', score_prize, 0)) as '语文',sum(IF(course_no = '0002', score_prize, 0)) as '数学',sum(IF(course_no = '0003', score_prize, 0)) as '英语'
from score
group by stu_no;

场景2：列转换行

1、准备数据表结构和数据

/*Navicat Premium Data TransferSource Server         : 本地Source Server Type    : MySQLSource Server Version : 80027Source Host           : localhost:3306Source Schema         : schoolTarget Server Type    : MySQLTarget Server Version : 80027File Encoding         : 65001Date: 13/06/2024 14:54:37
*/SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;-- ----------------------------
-- Table structure for cjs
-- ----------------------------
DROP TABLE IF EXISTS `cjs`;
CREATE TABLE `cjs`  (`name` varchar(32) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NULL DEFAULT NULL,`chinese` int NULL DEFAULT NULL,`math` int NULL DEFAULT NULL,`phy` int NULL DEFAULT NULL
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci ROW_FORMAT = Dynamic;-- ----------------------------
-- Records of cjs
-- ----------------------------
INSERT INTO `cjs` VALUES ('张三', 89, 90, 79);
INSERT INTO `cjs` VALUES ('李四', 88, 79, 90);SET FOREIGN_KEY_CHECKS = 1;

2、效果图

name	course
张三	90
张三	89
张三	79
李四	79
李四	88
李四	90

3、业务代码

select *
from (select name, math as coursefrom cjsunion allselect name, chinese as coursefrom cjsunion allselect name, phy as coursefrom cjs) t
order by t.name;