sql查询：行转列和列转行

水深无声 2023-10-05 12:54 59阅读 0赞

**目录**

一、行转列

1、使用case…when…then

2、使用SUM(IF()) 生成列

3、使用SUM(IF()) 生成列 + WITH ROLLUP 生成汇总行

4、使用SUM(IF()) 生成列，直接生成汇总结果，不再利用子查询

5、使用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

6、动态查询列值不确定的情况

7、合并字段显示：group\_concat()

二、列转行

--------------------

## 一、行转列 ##

将原本同一列下多行的不同内容作为多个字段，输出对应内容。

表及数据sql：

CREATE TABLE `tb_score` (
      `id` int(11) NOT NULL AUTO_INCREMENT,
      `userid` varchar(20) NOT NULL COMMENT '用户id',
      `subjectName` varchar(20) DEFAULT NULL COMMENT '科目',
      `score` double DEFAULT NULL COMMENT '成绩',
      PRIMARY KEY (`id`)
    ) ENGINE=InnoDB AUTO_INCREMENT=15 DEFAULT CHARSET=utf8;
    
    INSERT INTO `tb_score`(`id`, `userid`, `subjectName`, `score`) VALUES (1, '001', '语文', 90);
    INSERT INTO `tb_score`(`id`, `userid`, `subjectName`, `score`) VALUES (2, '001', '数学', 92);
    INSERT INTO `tb_score`(`id`, `userid`, `subjectName`, `score`) VALUES (3, '001', '英语', 80);
    INSERT INTO `tb_score`(`id`, `userid`, `subjectName`, `score`) VALUES (4, '002', '语文', 88);
    INSERT INTO `tb_score`(`id`, `userid`, `subjectName`, `score`) VALUES (5, '002', '数学', 90);
    INSERT INTO `tb_score`(`id`, `userid`, `subjectName`, `score`) VALUES (6, '002', '英语', 75.5);
    INSERT INTO `tb_score`(`id`, `userid`, `subjectName`, `score`) VALUES (7, '003', '语文', 70);
    INSERT INTO `tb_score`(`id`, `userid`, `subjectName`, `score`) VALUES (8, '003', '数学', 85);
    INSERT INTO `tb_score`(`id`, `userid`, `subjectName`, `score`) VALUES (9, '003', '英语', 90);
    INSERT INTO `tb_score`(`id`, `userid`, `subjectName`, `score`) VALUES (10, '003', '政治', 82);
    INSERT INTO `tb_score`(`id`, `userid`, `subjectName`, `score`) VALUES (11, '004', '政治', 82);
    INSERT INTO `tb_score`(`id`, `userid`, `subjectName`, `score`) VALUES (12, '004', '英语', 83);

行数据：

![20201030230539735.png][]

列数据：

![20201030231412900.png][]

### 1、使用case…when…then ###

SELECT
    	userid,
    	SUM( CASE subjectName WHEN '语文' THEN score ELSE 0 END ) '语文',
    	SUM( CASE subjectName WHEN '数学' THEN score ELSE 0 END ) '数学',
    	SUM( CASE subjectName WHEN '英语' THEN score ELSE 0 END ) '英语',
    	SUM( CASE subjectName WHEN '政治' THEN score ELSE 0 END ) '政治' 
    FROM
    	tb_score 
    GROUP BY
    	userid;

### 2、使用SUM(IF()) 生成列 ###

SELECT
    	userid,
    	SUM( IF ( subjectName = '语文', score, 0 ) ) '语文',
    	SUM( IF ( subjectName = '数学', score, 0 ) ) '数学',
    	SUM( IF ( subjectName = '英语', score, 0 ) ) '英语',
    	SUM( IF ( subjectName = '政治', score, 0 ) ) '政治' 
    FROM
    	tb_score 
    GROUP BY
    	userid;

### 3、使用SUM(IF()) 生成列 + WITH ROLLUP 生成汇总行 ###

MySQL提供了 group by with rollup 函数进行group by 字段的汇总，但是与order by 互斥的不能同时用。

SELECT
    	IFNULL( userid, 'total' ) AS userid,
    	SUM( IF ( subjectName = '语文', score, 0 ) ) '语文',
    	SUM( IF ( subjectName = '数学', score, 0 ) ) '数学',
    	SUM( IF ( subjectName = '英语', score, 0 ) ) '英语',
    	SUM( IF ( subjectName = '政治', score, 0 ) ) '政治',
    	SUM( IF ( subjectName = 'total', score, 0 ) ) AS 'total' 
    FROM
    	(
    		SELECT
    			userid,
    			IFNULL( subjectName, 'total' ) AS subjectName,
    			SUM( score ) AS score 
    		FROM
    			tb_score 
    		GROUP BY userid, subjectName WITH ROLLUP 
    	) AS a
    GROUP BY userid
    WITH ROLLUP;

### 4、使用SUM(IF()) 生成列，直接生成汇总结果，不再利用子查询 ###

SELECT IFNULL(userid,'total') AS userid,
    SUM(IF(subjectName='语文',score,0)) AS '语文',
    SUM(IF(subjectName='数学',score,0)) AS '数学',
    SUM(IF(subjectName='英语',score,0)) AS '英语',
    SUM(IF(subjectName='政治',score,0)) AS '政治',
    SUM(score) AS total
    FROM tb_score
    GROUP BY userid WITH ROLLUP;

### 5、使用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 userid,
    SUM(IF(subjectName='语文',score,0)) AS '语文',
    SUM(IF(subjectName='数学',score,0)) AS '数学',
    SUM(IF(subjectName='英语',score,0)) AS '英语',
    SUM(IF(subjectName='政治',score,0)) AS '政治',
    SUM(score) AS total
    FROM tb_score
    GROUP BY userid
    UNION
    SELECT 'total',SUM(IF(subjectName='语文',score,0)) AS '语文',
    SUM(IF(subjectName='数学',score,0)) AS '数学',
    SUM(IF(subjectName='英语',score,0)) AS '英语',
    SUM(IF(subjectName='政治',score,0)) AS '政治',
    SUM(score) FROM tb_score;

### 6、动态查询列值不确定的情况 ###

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

3、4、5、6、执行结果如下：

![2020103023451195.png][]

### 7、合并字段显示：group\_concat() ###

SELECT userid,GROUP_CONCAT(`subjectName`,":",score)AS 成绩 FROM tb_score GROUP BY userid;

group\_concat() 计算哪些行属于同一组，将属于同一组的列显示出来。要返回哪些列，由函数参数(就是字段名)决定。分组 是根据group by指定的列进行分组。

执行结果:

![20201031172639456.png][]

## 二、列转行 ##

CREATE TABLE tb_score1(
        id INT(11) NOT NULL auto_increment,
        userid VARCHAR(20) NOT NULL COMMENT '用户id',
        chinese_score DOUBLE COMMENT '语文成绩',
        math_score DOUBLE COMMENT '数学成绩',
        english_score DOUBLE COMMENT '英语成绩',
        politics_score DOUBLE COMMENT '政治成绩',
        PRIMARY KEY(id)
    )ENGINE = INNODB DEFAULT CHARSET = utf8;
    
    INSERT INTO tb_score1(userid,chinese_score,math_score,english_score,politics_score) VALUES ('001',90,92,80,0);
    INSERT INTO tb_score1(userid,chinese_score,math_score,english_score,politics_score) VALUES ('002',88,90,75.5,0);
    INSERT INTO tb_score1(userid,chinese_score,math_score,english_score,politics_score) VALUES ('003',70,85,90,82);
    INSERT INTO tb_score1(userid,chinese_score,math_score,english_score,politics_score) VALUES ('003',0,0,83,82);
    
    SELECT * FROM tb_score1;

查询结果：

![20201031211912760.png][]

列转行：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。

select userId,'语文' as subjectName,chinese_score as score from tb_score1
    union all
    select userId,'数学' as subjectName,math_score as score from tb_score1
    union all
    select userId,'英语' as subjectName,english_score as score from tb_score1
    union all
    select userId,'政治' as subjectName,politics_score as score from tb_score1;

转换后结果：

![20201031212724672.png][]

> **UNION** ： 会去掉重复记录,会排序,因为UNION 会做去重和排序处理,效率比UNION ALL慢很多。

> **UNION ALL** ：不会对结果进行去重处理，只是简单地将两个结果集合并。

参考文章：

[一篇文章搞定mysql的 行转列（7种方法） 和 列转行][mysql_ _7_ _]

[20201030230539735.png]: https://img-blog.csdnimg.cn/20201030230539735.png
[20201030231412900.png]: https://img-blog.csdnimg.cn/20201030231412900.png
[2020103023451195.png]: https://img-blog.csdnimg.cn/2020103023451195.png
[20201031172639456.png]: https://img-blog.csdnimg.cn/20201031172639456.png
[20201031211912760.png]: https://img-blog.csdnimg.cn/20201031211912760.png
[20201031212724672.png]: https://img-blog.csdnimg.cn/20201031212724672.png
[mysql_ _7_ _]: https://blog.csdn.net/weter_drop/article/details/105899362?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522160406988919724838506659%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fblog.%2522%257D&request_id=160406988919724838506659&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~blog~first_rank_v1~rank_blog_v1-1-105899362.pc_v1_rank_blog_v1&utm_term=%E8%A1%8C%E8%BD%AC%E5%88%97&spm=1018.2118.3001.4450