mysql 行列轉換，行轉列和列轉行

目錄

行轉列

列轉行

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行轉列

建立測試表，添加測試數據

DROP TABLE IF EXISTS `score`;
CREATE TABLE `score` (
  `subject` varchar(255) DEFAULT NULL,
  `score` int(11) DEFAULT NULL,
  `stu_id` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of score
-- ----------------------------
INSERT INTO `score` VALUES ('語文', '88', '101');
INSERT INTO `score` VALUES ('語文', '90', '2');
INSERT INTO `score` VALUES ('語文', '78', '3');
INSERT INTO `score` VALUES ('數學', '93', '3');
INSERT INTO `score` VALUES ('數學', '89', '101');
INSERT INTO `score` VALUES ('數學', '98', '2');
INSERT INTO `score` VALUES ('英語', '99', '2');
INSERT INTO `score` VALUES ('英語', '69', '3');
INSERT INTO `score` VALUES ('英語', '96', '101');
INSERT INTO `score` VALUES ('英語', '99', '4');

表數據結構如圖：

效果圖：

1、使用case when

SELECT stu_id,
sum(case when subject='語文' then score else 0 end) as '語文',
sum(case when subject='數學' then score else 0 end) as '數學',
sum(case when subject='英語' then score else 0 end) as '英語'
 FROM score GROUP BY stu_id;

2、使用if

SELECT stu_id,
sum(if(subject='語文',score,0 )) as '語文',
sum(if(subject='數學',score,0 )) as '數學',
sum(if(subject='英語',score,0 )) as '英語'
 FROM score GROUP BY stu_id;

列轉行

建立測試表，添加測試數據

DROP TABLE IF EXISTS `score`;
CREATE TABLE `score` (
  `stu_id` int(11) DEFAULT NULL,
  `chinese_score` int(11) DEFAULT NULL,
  `math_score` int(11) DEFAULT NULL,
  `english_score` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of score
-- ----------------------------
INSERT INTO `score` VALUES ('101', '80', '90', '100');
INSERT INTO `score` VALUES ('102', '88', '78', '99');
INSERT INTO `score` VALUES ('103', '69', '98', '87');

表數據結構如圖：

列轉行sql：

SELECT stu_id,'語文' AS course,chinese_score AS score FROM score
UNION ALL
SELECT stu_id,'數學' AS course,math_score AS score FROM score
UNION ALL
SELECT stu_id,'外語' AS course,english_score AS score FROM score
ORDER BY stu_id

轉換效果：