MYSQL行列转置方式

CREATE TABLE grade
(
	stuName VARCHAR(20) NOT NULL COMMENT '学生姓名',
	stuCourse VARCHAR(20) NOT NULL COMMENT '学生课程名',
	stuScore INT NOT NULL COMMENT '学生课程分数'
)

INSERT INTO grade(stuName,stuCourse,stuScore)
VALUES
('张三','语文',110),
('张三','数学',130),
('张三','英语',60),
('张三','体育',40),
('李四','语文',108),
('李四','数学',145),
('李四','英语',28),
('李四','体育',48),
('王五','语文',120),
('王五','数学',99),
('王五','英语',140),
('王五','体育',42)

SELECT * FROM grade

CASE case_value
	WHEN when_value THEN
		statement_list
	ELSE
		statement_list
END CASE;

SELECT stuName,
SUM(CASE WHEN stuCourse='语文' THEN stuScore ELSE 0 END) AS '语文',
SUM(CASE WHEN stuCourse='数学' THEN stuScore ELSE 0 END) AS '数学',
SUM(CASE WHEN stuCourse='英语' THEN stuScore ELSE 0 END) AS '英语',
SUM(CASE WHEN stuCourse='体育' THEN stuScore ELSE 0 END) AS '体育',
SUM(stuScore) AS '学科总分'
FROM grade
GROUP BY stuName

//SELECT 后跟查询结果
SELECT stuName, 
//SUM 聚合函数（官方写好求和用的） 
// CASE WHEN stuCourse='语文' THEN stuScore ELSE 0 END 
用于替换值 若stuCourse='语文' 则对应显示stuScore，否则显示0
//AS 重命名 列/（也叫字段）名
SUM(CASE WHEN stuCourse='语文' THEN stuScore ELSE 0 END) AS '语文',
SUM(CASE WHEN stuCourse='数学' THEN stuScore ELSE 0 END) AS '数学',
SUM(CASE WHEN stuCourse='英语' THEN stuScore ELSE 0 END) AS '英语',
SUM(CASE WHEN stuCourse='体育' THEN stuScore ELSE 0 END) AS '体育',
//SUM(stuScore)求各个学科总分数
SUM(stuScore) AS '学科总分'
//from 后跟要查询的表名
FROM grade
//GROUP BY 对stuName进行分组，没有这句，会报错，要不然，就是显示第一行
GROUP BY stuName

IF(expr1,expr2,expr3)

SELECT stuName,
SUM(IF(stuCourse='语文',stuScore,0)) AS '语文',
SUM(IF(stuCourse='数学',stuScore,0)) AS '数学',
SUM(IF(stuCourse='英语',stuScore,0)) AS '英语',
SUM(IF(stuCourse='体育',stuScore,0)) AS '体育',
SUM(stuScore) AS '学科总分'
FROM grade
GROUP BY stuName