mysql怎么合并行

CREATE TABLE students (
    id INT PRIMARY KEY,
    name VARCHAR(100),
    subject VARCHAR(100)
);

INSERT INTO students (id, name, subject) VALUES
(1, 'Alice', 'Math'),
(2, 'Alice', 'Science'),
(3, 'Bob', 'Math');

SELECT name, GROUP_CONCAT(subject SEPARATOR ', ') AS subjects
FROM students
GROUP BY name;

+-------+------------------+
| name  | subjects         |
+-------+------------------+
| Alice | Math, Science    |
| Bob   | Math             |
+-------+------------------+

SELECT name, JSON_ARRAYAGG(subject) AS subjects
FROM students
GROUP BY name;

+-------+------------------+
| name  | subjects         |
+-------+------------------+
| Alice | ["Math", "Science"] |
| Bob   | ["Math"]          |
+-------+------------------+

SELECT name, STRING_AGG(subject, ', ' ORDER BY subject) AS subjects
FROM students
GROUP BY name;

+-------+------------------+
| name  | subjects         |
+-------+------------------+
| Alice | Math, Science    |
| Bob   | Math             |
+-------+------------------+

CREATE TABLE orders (
    id INT PRIMARY KEY,
    customer_id INT,
    product VARCHAR(100)
);

INSERT INTO orders (id, customer_id, product) VALUES
(1, 1, 'Laptop'),
(2, 1, 'Phone'),
(3, 2, 'Tablet');

SELECT customer_id, GROUP_CONCAT(product SEPARATOR ', ') AS products
FROM orders
GROUP BY customer_id;

+-------------+------------------+
| customer_id | products         |
+-------------+------------------+
|           1 | Laptop, Phone    |
|           2 | Tablet           |
+-------------+------------------+