MySQL ON 子句中的未知列

MySQL中的ON子句是用于在连接两个或多个表时指定连接条件的一种语法结构。通常，在使用JOIN操作连接表时，我们需要指定连接条件，以便从多个表中获取所需的数据。ON子句就是用来提供这些连接条件的。

sql
SELECT 列名
FROM 表1
JOIN 表2
ON 连接条件;

sql
CREATE TABLE students (
    id INT PRIMARY KEY,
    name VARCHAR(50)
);
CREATE TABLE scores (
    student_id INT,
    subject VARCHAR(50),
    score INT
);
INSERT INTO students (id, name) VALUES (1, '张三');
INSERT INTO students (id, name) VALUES (2, '李四');
INSERT INTO students (id, name) VALUES (3, '王五');
INSERT INTO scores (student_id, subject, score) VALUES (1, '数学', 90);
INSERT INTO scores (student_id, subject, score) VALUES (1, '英语', 85);
INSERT INTO scores (student_id, subject, score) VALUES (2, '数学', 95);
INSERT INTO scores (student_id, subject, score) VALUES (2, '英语', 92);
INSERT INTO scores (student_id, subject, score) VALUES (3, '数学', 88);
INSERT INTO scores (student_id, subject, score) VALUES (3, '英语', 90);

sql
SELECT students.name, SUM(scores.score) AS total_score
FROM students
JOIN scores
ON students.id = scores.student_id
GROUP BY students.name;