Mysql行转列，列转行 WITH ROLLUP 统计

DROP TABLE IF EXISTS tb_score;

CREATE TABLE tb_score(
    id INT(11) NOT NULL AUTO_INCREMENT,
    userid VARCHAR(20) NOT NULL COMMENT '用户id',
    SUBJECT VARCHAR(20) COMMENT '科目',
    score DOUBLE COMMENT '成绩',
    PRIMARY KEY(id)
)ENGINE = INNODB DEFAULT CHARSET = utf8;

INSERT INTO tb_score(userid,SUBJECT,score) VALUES ('001','语文',90);
INSERT INTO tb_score(userid,SUBJECT,score) VALUES ('001','数学',92);
INSERT INTO tb_score(userid,SUBJECT,score) VALUES ('001','英语',80);
INSERT INTO tb_score(userid,SUBJECT,score) VALUES ('002','语文',88);
INSERT INTO tb_score(userid,SUBJECT,score) VALUES ('002','数学',90);
INSERT INTO tb_score(userid,SUBJECT,score) VALUES ('002','英语',75.5);
INSERT INTO tb_score(userid,SUBJECT,score) VALUES ('003','语文',70);
INSERT INTO tb_score(userid,SUBJECT,score) VALUES ('003','数学',85);
INSERT INTO tb_score(userid,SUBJECT,score) VALUES ('003','英语',90);
INSERT INTO tb_score(userid,SUBJECT,score) VALUES ('003','政治',82);

SELECT * FROM tb_score

## 行转列   WITH ROLLUP 统计
# 1、使用case...when....then 进行行转列
SELECT userid,
SUM(CASE `subject` WHEN '语文' THEN score ELSE 0 END) AS '语文',
SUM(CASE `subject` WHEN '数学' THEN score ELSE 0 END) AS '数学',
SUM(CASE `subject` WHEN '英语' THEN score ELSE 0 END) AS '英语',
SUM(CASE `subject` WHEN '政治' THEN score ELSE 0 END) AS '政治' 
FROM tb_score 
GROUP BY userid

# 2、使用IF() 进行行转列：
SELECT userid,
SUM(IF(`subject`='语文',score,0)) AS '语文',
SUM(IF(`subject`='数学',score,0)) AS '数学',
SUM(IF(`subject`='英语',score,0)) AS '英语',
SUM(IF(`subject`='政治',score,0)) AS '政治' 
FROM tb_score 
GROUP BY userid

# 3、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(userid,'total') AS userid,
SUM(IF(`subject`='语文',score,0)) AS 语文,
SUM(IF(`subject`='数学',score,0)) AS 数学,
SUM(IF(`subject`='英语',score,0)) AS 英语,
SUM(IF(`subject`='政治',score,0)) AS 政治,
SUM(IF(`subject`='total',score,0)) AS total
FROM(
    SELECT userid,IFNULL(`subject`,'total') AS `subject`,SUM(score) AS score
    FROM tb_score
    GROUP BY userid,`subject`
    WITH ROLLUP
    HAVING userid IS NOT NULL
)AS A 
GROUP BY userid
WITH ROLLUP;

## 行统计
SELECT userid,
SUM(IF(`subject`='语文',score,0)) AS 语文,
SUM(IF(`subject`='数学',score,0)) AS 数学,
SUM(IF(`subject`='英语',score,0)) AS 英语,
SUM(IF(`subject`='政治',score,0)) AS 政治,
SUM(IF(`subject`='total',score,0)) AS total
FROM(
    SELECT userid,IFNULL(`subject`,'total') AS `subject`,SUM(score) AS score
    FROM tb_score
    GROUP BY userid,`subject`
    WITH ROLLUP
    HAVING userid IS NOT NULL
)AS A 
GROUP BY userid
WITH ROLLUP
HAVING userid IS NOT NULL

## 列统计
SELECT IFNULL(userid,'total') AS userid,
SUM(IF(`subject`='语文',score,0)) AS 语文,
SUM(IF(`subject`='数学',score,0)) AS 数学,
SUM(IF(`subject`='英语',score,0)) AS 英语,
SUM(IF(`subject`='政治',score,0)) AS 政治
FROM(
    SELECT userid,IFNULL(`subject`,'total') AS `subject`,SUM(score) AS score
    FROM tb_score
    GROUP BY userid,`subject`
)AS A 
GROUP BY userid
WITH ROLLUP

# 4、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 userid,
SUM(IF(`subject`='语文',score,0)) AS 语文,
SUM(IF(`subject`='数学',score,0)) AS 数学,
SUM(IF(`subject`='英语',score,0)) AS 英语,
SUM(IF(`subject`='政治',score,0)) AS 政治,
SUM(score) AS TOTAL 
FROM tb_score
GROUP BY userid
UNION
SELECT 'TOTAL',SUM(IF(`subject`='语文',score,0)) AS 语文,
SUM(IF(`subject`='数学',score,0)) AS 数学,
SUM(IF(`subject`='英语',score,0)) AS 英语,
SUM(IF(`subject`='政治',score,0)) AS 政治,
SUM(score) FROM tb_score

## 5、利用SUM(IF()) 生成列，直接生成结果不再利用子查询
SELECT IFNULL(userid,'TOTAL') AS userid,
SUM(IF(`subject`='语文',score,0)) AS 语文,
SUM(IF(`subject`='数学',score,0)) AS 数学,
SUM(IF(`subject`='英语',score,0)) AS 英语,
SUM(IF(`subject`='政治',score,0)) AS 政治,
SUM(score) AS TOTAL 
FROM tb_score
GROUP BY userid WITH ROLLUP;

## 6、动态，适用于列不确定情况  ?? 以下语句需要一行一行执行
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;

## 7、合并字段显示：利用group_concat()
SELECT userid,GROUP_CONCAT(`subject`,":",score)AS 成绩 FROM tb_score
GROUP BY userid
## 结论：group_concat()函数可以很好的建属于同一分组的多个行转化为一个列。


## 列转行
CREATE TABLE tb_score1(
    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_score1(userid,cn_score,math_score,en_score,po_score) VALUES ('001',90,92,80,0);
INSERT INTO tb_score1(userid,cn_score,math_score,en_score,po_score) VALUES ('002',88,90,75.5,0);
INSERT INTO tb_score1(userid,cn_score,math_score,en_score,po_score) VALUES ('003',70,85,90,82);

SELECT * FROM tb_score1

SELECT userid,'语文' AS course,cn_score AS score FROM tb_score1
UNION ALL
SELECT userid,'数学' AS course,math_score AS score FROM tb_score1
UNION ALL
SELECT userid,'英语' AS course,en_score AS score FROM tb_score1
UNION ALL
SELECT userid,'政治' AS course,po_score AS score FROM tb_score1
ORDER BY userid  ## 写在最后，不然也可以查询出来。不过结果未排序

/**
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；
转载： https://www.cnblogs.com/xiaoxi/p/7151433.html
**/