行转列

CREATE TABLE students_score(
    cname VARCHAR(10),
    course VARCHAR(10),
    score INT(6)
);

INSERT INTO students_score VALUES
('张三','语文',74),
('张三','数学',83),
('张三','物理',93),
('李四','语文',65),
('李四','数学',87),
('李四','物理',90);
 
CREATE TABLE student(
    stu_id INT(4) UNSIGNED PRIMARY KEY AUTO_INCREMENT,
    stu_name VARCHAR(20)
);
 
INSERT INTO student(stu_name) VALUES
('张三'),('李四');

原表的输出结果如下：

经过行转列之后，也就是说分别合并张三和李四的四行变两行

SELECT cname 姓名,
MAX(CASE course WHEN '语文' THEN score ELSE 0 END ) 语文,
MAX(CASE course WHEN '数学' THEN score ELSE 0 END ) 数学,
MAX(CASE course WHEN '物理' THEN score ELSE 0 END ) 物理
FROM students_score
GROUP BY cname;