MySql行转列 以及列转行

行转列

• sql脚本

CREATE TABLE `score` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(40) COLLATE utf8mb4_bin DEFAULT NULL,
  `subject` varchar(255) COLLATE utf8mb4_bin DEFAULT NULL,
  `score` int(255) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;

-- ----------------------------
-- Records of score
-- ----------------------------
BEGIN;
INSERT INTO `score` VALUES (1, '张三', '语文', 80);
INSERT INTO `score` VALUES (2, '张三', '数学', 85);
INSERT INTO `score` VALUES (3, '张三', '英语', 90);
INSERT INTO `score` VALUES (4, '李四', '语文', 60);
INSERT INTO `score` VALUES (5, '李四', '数学', 50);
INSERT INTO `score` VALUES (6, '李四', '英语', 70);
COMMIT;

• 代码实现

-- 行转列
select NAME,
MAX(CASE SUBJECT WHEN '语文' then score end ) '语文',
MAX(CASE SUBJECT WHEN '数学' THEN score END) '数学',
MAX(CASE SUBJECT WHEN '英语' THEN score END) '英语'
from score GROUP BY NAME

• 结果
  

列转行

• sql脚本

CREATE TABLE `score2` (
  `id` int(255) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) COLLATE utf8mb4_bin DEFAULT NULL,
  `yw_score` int(5) DEFAULT NULL,
  `sx_score` int(5) DEFAULT NULL,
  `yy_score` int(5) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;

-- ----------------------------
-- Records of score2
-- ----------------------------
BEGIN;
INSERT INTO `score2` VALUES (1, '张三', 80, 90, 85);
INSERT INTO `score2` VALUES (2, '李四', 70, 50, 80);
COMMIT;

• 代码实现

-- 自定义常量,先执行定义变量的代码，再执行列转行的代码
set @num:=0;

select @num
-- 列转行
select @num:=@num +1 'id', NAME, '语文' as 'subject', yw_score as SCORE from score2
UNION
select @num:=@num +1 'id', NAME, '数学' as 'subject', sx_score as SCORE from score2
UNION
select @num:=@num +1 'id', NAME ,'英语' as 'subject', yy_score as SCORE from score2