mysql行转列列转行

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工作中经常用到的mysql行转列和列转行总结

一、行转列

创建数据表和创建数据

CREATE TABLE `student` (
  `name` varchar() DEFAULT NULL COMMENT '名字',
  `subject` varchar() DEFAULT NULL COMMENT '科目',
  `score` float DEFAULT NULL COMMENT '分数'
) ENGINE=InnoDB DEFAULT CHARSET=utf8

INSERT INTO student (NAME,SUBJECT,score) 
VALUES
('张三', '语文', 80),
('张三', '数学', 90),
('张三', '英语', 70),
('张三', '生物', 85),
('李四', '语文', 80),
( '李四', '数学', 92),
(  '李四', '英语', 76),
('李四', '生物', 88),
(  '码农', '语文', 60),
('码农', '数学', 82),
( '码农', '英语', 96),
( '码农', '生物', 78);

查询数据表中的内容（即转换前的结果）
```
SELECT * FROM student
```
先来看一下转换后的结果

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

SELECT IFNULL(NAME,'total') AS NAME,
SUM(IF(`subject`='数学',score,0)) AS '数学',
SUM(IF(`subject`='语文',score,0)) AS '语文',
SUM(IF(`subject`='英语',score,0)) AS '英语',
SUM(IF(`subject`='生物',score,0)) AS '生物', 
SUM(IF(`subject`='total',score,0)) AS total
FROM(
    SELECT NAME,IFNULL(`subject`,'total') AS `subject`,SUM(score) AS score
    FROM student
    GROUP BY NAME,`subject`
    WITH ROLLUP
    HAVING NAME IS NOT NULL
)AS A 
GROUP BY NAME
WITH ROLLUP;

运行结果：

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

SELECT NAME,
SUM(IF(`subject`='数学',score,0)) AS '数学',
SUM(IF(`subject`='语文',score,0)) AS '语文',
SUM(IF(`subject`='英语',score,0)) AS '英语',
SUM(IF(`subject`='生物',score,0)) AS '生物', 
SUM(score) AS TOTAL 
FROM student
GROUP BY NAME
UNION
SELECT 'TOTAL',
SUM(IF(`subject`='数学',score,0)) AS '数学',
SUM(IF(`subject`='语文',score,0)) AS '语文',
SUM(IF(`subject`='英语',score,0)) AS '英语',
SUM(IF(`subject`='生物',score,0)) AS '生物', 
SUM(score) FROM student

运行结果：

利用SUM(IF()) 生成列，直接生成结果不再利用子查询

SELECT IFNULL(NAME,'TOTAL') AS NAME,
SUM(IF(`subject`='数学',score,0)) AS '数学',
SUM(IF(`subject`='语文',score,0)) AS '语文',
SUM(IF(`subject`='英语',score,0)) AS '英语',
SUM(IF(`subject`='生物',score,0)) AS '生物', 
SUM(score) AS TOTAL 
FROM student
GROUP BY NAME WITH ROLLUP;

运行结果：

动态，适用于列不确定情况

SET @EE='';
SELECT @EE :=CONCAT(@EE,'sum(if(subject= \'',SUBJECT,'\',score,0)) as ',SUBJECT, ',') AS aa FROM (SELECT DISTINCT SUBJECT FROM student) A ;
 
SET @QQ = CONCAT('select ifnull(name,\'TOTAL\')as name,',@EE,' sum(score) as TOTAL from student group by name WITH ROLLUP');
-- SELECT @QQ;
 
PREPARE stmt FROM @QQ;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

运行结果：

合并字段显示：利用group_concat()

SELECT NAME,GROUP_CONCAT(`subject`,":",score)AS 成绩 FROM student
GROUP BY NAME

运行结果：

二、列转行

创建数据表和创建数据

CREATE TABLE tb_score(
    id INT(11) NOT NULL AUTO_INCREMENT,
    userid VARCHAR(20) NOT NULL COMMENT '用户id',
    cn_score DOUBLE COMMENT '语文成绩',
    math_score DOUBLE COMMENT '数学成绩',
    en_score DOUBLE COMMENT '英语成绩',
    po_score DOUBLE COMMENT '政治成绩',
    PRIMARY KEY(id)
)ENGINE = INNODB DEFAULT CHARSET = utf8;

INSERT INTO tb_score (userid,cn_score,math_score,en_score,po_score) 
VALUES 
('001',90,92,80,0),
('002',88,90,75.5,0),
('003',70,85,90,82);

查询数据表中的内容（即转换前的结果）
```
SELECT * FROM tb_score
```
转换后：

UNION ALL

SELECT userid,'语文' AS course,cn_score AS score FROM tb_score
UNION ALL
SELECT userid,'数学' AS course,math_score AS score FROM tb_score
UNION ALL
SELECT userid,'英语' AS course,en_score AS score FROM tb_score
UNION ALL
SELECT userid,'政治' AS course,po_score AS score FROM tb_score
ORDER BY userid

UNION

SELECT userid, '政治' COURSE, PO_SCORE AS SCORE FROM tb_score
UNION 
SELECT userid, '英语' COURSE, EN_SCORE AS SCORE FROM tb_score
UNION 
SELECT userid, '数学' COURSE, MATH_SCORE AS SCORE FROM tb_score
UNION 
SELECT userid, '语文' COURSE , CN_SCORE AS SCORE FROM tb_score
ORDER BY userid,COURSE;

这里将每个userid对应的多个科目的成绩查出来，通过UNION ALL将结果集加起来，达到上图的效果。
附：UNION与UNION ALL的区别（摘）：
1.对重复结果的处理：UNION会去掉重复记录，UNION ALL不会；
2.对排序的处理：UNION会排序，UNION ALL只是简单地将两个结果集合并；
3.效率方面的区别：因为UNION 会做去重和排序处理，因此效率比UNION ALL慢很多；

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mysql行转列 列转行

工作中经常用到的mysql行转列和列转行总结

mysql行转列列转行